Add instructions to setup API key

.github/workflows/deploy_dev_docs.yaml

@@ -40,7 +40,7 @@ jobs:
       group: docs-deployment
       cancel-in-progress: false
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           fetch-depth: 0 # Fetch all history for .GitInfo and .Lastmod
 
@@ -56,7 +56,7 @@ jobs:
           node-version: "22"
 
       - name: Cache dependencies
-        uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5
+        uses: actions/cache@8b402f58fbc84540c8b491a91e594a4576fec3d7 # v5
         with:
           path: ~/.npm
           key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}

.github/workflows/deploy_previous_version_docs.yaml

@@ -30,14 +30,14 @@ jobs:
 
     steps:
       - name: Checkout main branch (for latest templates and theme)
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           ref: 'main'
           submodules: 'recursive'
           fetch-depth: 0
 
       - name: Checkout old content from tag into a temporary directory
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           ref: ${{ github.event.inputs.version_tag }}
           path: 'old_version_source' # Checkout into a temp subdir

.github/workflows/deploy_versioned_docs.yaml

@@ -30,7 +30,7 @@ jobs:
       cancel-in-progress: false
     steps:
       - name: Checkout Code at Tag
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           ref: ${{ github.event.release.tag_name }}
 

.github/workflows/docs_preview_clean.yaml

@@ -34,7 +34,7 @@ jobs:
       group: "preview-${{ github.event.number }}"
       cancel-in-progress: true
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           ref: versioned-gh-pages
 

.github/workflows/docs_preview_deploy.yaml

@@ -49,7 +49,7 @@ jobs:
       group: "preview-${{ github.event.number }}"
       cancel-in-progress: true
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
         with:
           # Checkout the PR's HEAD commit (supports forks).
           ref: ${{ github.event.pull_request.head.sha }}
@@ -67,7 +67,7 @@ jobs:
           node-version: "22"
 
       - name: Cache dependencies
-        uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5
+        uses: actions/cache@8b402f58fbc84540c8b491a91e594a4576fec3d7 # v5
         with:
           path: ~/.npm
           key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}

.github/workflows/link_checker_workflow.yaml

@@ -22,10 +22,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
 
       - name: Restore lychee cache
-        uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5
+        uses: actions/cache@8b402f58fbc84540c8b491a91e594a4576fec3d7 # v5
         with:
           path: .lycheecache
           key: cache-lychee-${{ github.sha }}

.github/workflows/publish-mcp.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
 
       - name: Wait for image in Artifact Registry
         shell: bash

docs/en/getting-started/local_quickstart_go.md

@@ -46,6 +46,11 @@ from Toolbox.
     go get github.com/googleapis/mcp-toolbox-sdk-go
     ```
 
+1. Set your API key (If you don't have an API key yet, you can get one from [Google AI Studio](https://aistudio.google.com/app/apikey).)
+   ```bash
+   export GOOGLE_API_KEY="YOUR_ACTUAL_GEMINI_API_KEY"
+   ```
+
 1. Create a new file named `hotelagent.go` and copy the following code to create
    an agent:
 

internal/server/api.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
@@ -233,11 +234,10 @@ func toolInvokeHandler(s *Server, w http.ResponseWriter, r *http.Request) {
 
 	params, err := parameters.ParseParams(tool.GetParameters(), data, claimsFromAuth)
 	if err != nil {
-		// If auth error, return 401 or 403
-		var clientServerErr *util.ClientServerError
-		if errors.As(err, &clientServerErr) && (clientServerErr.Code == http.StatusUnauthorized || clientServerErr.Code == http.StatusForbidden) {
+		// If auth error, return 401
+		if errors.Is(err, util.ErrUnauthorized) {
 			s.logger.DebugContext(ctx, fmt.Sprintf("error parsing authenticated parameters from ID token: %s", err))
-			_ = render.Render(w, r, newErrResponse(err, clientServerErr.Code))
+			_ = render.Render(w, r, newErrResponse(err, http.StatusUnauthorized))
 			return
 		}
 		err = fmt.Errorf("provided parameters were invalid: %w", err)
@@ -259,49 +259,34 @@ func toolInvokeHandler(s *Server, w http.ResponseWriter, r *http.Request) {
 
 	// Determine what error to return to the users.
 	if err != nil {
-		var tbErr util.ToolboxError
+		errStr := err.Error()
+		var statusCode int
 
-		if errors.As(err, &tbErr) {
-			switch tbErr.Category() {
-			case util.CategoryAgent:
-				// Agent Errors -> 200 OK
-				s.logger.DebugContext(ctx, fmt.Sprintf("Tool invocation agent error: %v", err))
-				_ = render.Render(w, r, newErrResponse(err, http.StatusOK))
-				return
+		// Upstream API auth error propagation
+		switch {
+		case strings.Contains(errStr, "Error 401"):
+			statusCode = http.StatusUnauthorized
+		case strings.Contains(errStr, "Error 403"):
+			statusCode = http.StatusForbidden
+		}
 
-			case util.CategoryServer:
-				// Server Errors -> Check the specific code inside
-				var clientServerErr *util.ClientServerError
-				statusCode := http.StatusInternalServerError // Default to 500
-
-				if errors.As(err, &clientServerErr) {
-					if clientServerErr.Code != 0 {
-						statusCode = clientServerErr.Code
-					}
-				}
-
-				// Process auth error
-				if statusCode == http.StatusUnauthorized || statusCode == http.StatusForbidden {
-					if clientAuth {
-						// Token error, pass through 401/403
-						s.logger.DebugContext(ctx, fmt.Sprintf("Client credentials lack authorization: %v", err))
-						_ = render.Render(w, r, newErrResponse(err, statusCode))
-						return
-					}
-					// ADC/Config error, return 500
-					statusCode = http.StatusInternalServerError
-				}
-
-				s.logger.ErrorContext(ctx, fmt.Sprintf("Tool invocation server error: %v", err))
+		if statusCode == http.StatusUnauthorized || statusCode == http.StatusForbidden {
+			if clientAuth {
+				// Propagate the original 401/403 error.
+				s.logger.DebugContext(ctx, fmt.Sprintf("error invoking tool. Client credentials lack authorization to the source: %v", err))
 				_ = render.Render(w, r, newErrResponse(err, statusCode))
 				return
 			}
-		} else {
-			// Unknown error -> 500
-			s.logger.ErrorContext(ctx, fmt.Sprintf("Tool invocation unknown error: %v", err))
-			_ = render.Render(w, r, newErrResponse(err, http.StatusInternalServerError))
+			// ADC lacking permission or credentials configuration error.
+			internalErr := fmt.Errorf("unexpected auth error occured during Tool invocation: %w", err)
+			s.logger.ErrorContext(ctx, internalErr.Error())
+			_ = render.Render(w, r, newErrResponse(internalErr, http.StatusInternalServerError))
 			return
 		}
+		err = fmt.Errorf("error while invoking tool: %w", err)
+		s.logger.DebugContext(ctx, err.Error())
+		_ = render.Render(w, r, newErrResponse(err, http.StatusBadRequest))
+		return
 	}
 
 	resMarshal, err := json.Marshal(res)

internal/server/common_test.go

@@ -30,7 +30,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/server/resources"
 	"github.com/googleapis/genai-toolbox/internal/telemetry"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -52,7 +51,7 @@ type MockTool struct {
 	requiresClientAuthrorization bool
 }
 
-func (t MockTool) Invoke(context.Context, tools.SourceProvider, parameters.ParamValues, tools.AccessToken) (any, util.ToolboxError) {
+func (t MockTool) Invoke(context.Context, tools.SourceProvider, parameters.ParamValues, tools.AccessToken) (any, error) {
 	mock := []any{t.Name}
 	return mock, nil
 }

internal/server/mcp.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
@@ -443,12 +444,15 @@ func httpHandler(s *Server, w http.ResponseWriter, r *http.Request) {
 		code := rpcResponse.Error.Code
 		switch code {
 		case jsonrpc.INTERNAL_ERROR:
-			// Map Internal RPC Error (-32603) to HTTP 500
 			w.WriteHeader(http.StatusInternalServerError)
 		case jsonrpc.INVALID_REQUEST:
-			var clientServerErr *util.ClientServerError
-			if errors.As(err, &clientServerErr) {
-				w.WriteHeader(clientServerErr.Code)
+			errStr := err.Error()
+			if errors.Is(err, util.ErrUnauthorized) {
+				w.WriteHeader(http.StatusUnauthorized)
+			} else if strings.Contains(errStr, "Error 401") {
+				w.WriteHeader(http.StatusUnauthorized)
+			} else if strings.Contains(errStr, "Error 403") {
+				w.WriteHeader(http.StatusForbidden)
 			}
 		}
 	}

internal/server/mcp/v20241105/method.go

@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -123,12 +124,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			errMsg := "missing access token in the 'Authorization' header"
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, errMsg, nil), util.NewClientServerError(
-				errMsg,
-				http.StatusUnauthorized,
-				nil,
-			)
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
 		}
 	}
 
@@ -176,11 +172,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// Check if any of the specified auth services is verified
 	isAuthorized := tool.Authorized(verifiedAuthServices)
 	if !isAuthorized {
-		err = util.NewClientServerError(
-			"unauthorized Tool call: Please make sure you specify correct auth headers",
-			http.StatusUnauthorized,
-			nil,
-		)
+		err = fmt.Errorf("unauthorized Tool call: Please make sure your specify correct auth headers: %w", util.ErrUnauthorized)
 		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
@@ -202,44 +194,30 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// run tool invocation and generate response.
 	results, err := tool.Invoke(ctx, resourceMgr, params, accessToken)
 	if err != nil {
-		var tbErr util.ToolboxError
-
-		if errors.As(err, &tbErr) {
-			switch tbErr.Category() {
-			case util.CategoryAgent:
-				// MCP - Tool execution error
-				// Return SUCCESS but with IsError: true
-				text := TextContent{
-					Type: "text",
-					Text: err.Error(),
-				}
-				return jsonrpc.JSONRPCResponse{
-					Jsonrpc: jsonrpc.JSONRPC_VERSION,
-					Id:      id,
-					Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
-				}, nil
-
-			case util.CategoryServer:
-				// MCP Spec - Protocol error
-				// Return JSON-RPC ERROR
-				var clientServerErr *util.ClientServerError
-				rpcCode := jsonrpc.INTERNAL_ERROR // Default to Internal Error (-32603)
-
-				if errors.As(err, &clientServerErr) {
-					if clientServerErr.Code == http.StatusUnauthorized || clientServerErr.Code == http.StatusForbidden {
-						if clientAuth {
-							rpcCode = jsonrpc.INVALID_REQUEST
-						} else {
-							rpcCode = jsonrpc.INTERNAL_ERROR
-						}
-					}
-				}
-				return jsonrpc.NewError(id, rpcCode, err.Error(), nil), err
+		errStr := err.Error()
+		// Missing authService tokens.
+		if errors.Is(err, util.ErrUnauthorized) {
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
+		}
+		// Upstream auth error
+		if strings.Contains(errStr, "Error 401") || strings.Contains(errStr, "Error 403") {
+			if clientAuth {
+				// Error with client credentials should pass down to the client
+				return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 			}
-		} else {
-			// Unknown error -> 500
+			// Auth error with ADC should raise internal 500 error
 			return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
 		}
+
+		text := TextContent{
+			Type: "text",
+			Text: err.Error(),
+		}
+		return jsonrpc.JSONRPCResponse{
+			Jsonrpc: jsonrpc.JSONRPC_VERSION,
+			Id:      id,
+			Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
+		}, nil
 	}
 
 	content := make([]TextContent, 0)

internal/server/mcp/v20250326/method.go

@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -123,12 +124,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			errMsg := "missing access token in the 'Authorization' header"
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, errMsg, nil), util.NewClientServerError(
-				errMsg,
-				http.StatusUnauthorized,
-				nil,
-			)
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
 		}
 	}
 
@@ -176,11 +172,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// Check if any of the specified auth services is verified
 	isAuthorized := tool.Authorized(verifiedAuthServices)
 	if !isAuthorized {
-		err = util.NewClientServerError(
-			"unauthorized Tool call: Please make sure you specify correct auth headers",
-			http.StatusUnauthorized,
-			nil,
-		)
+		err = fmt.Errorf("unauthorized Tool call: Please make sure your specify correct auth headers: %w", util.ErrUnauthorized)
 		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
@@ -202,45 +194,31 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// run tool invocation and generate response.
 	results, err := tool.Invoke(ctx, resourceMgr, params, accessToken)
 	if err != nil {
-		var tbErr util.ToolboxError
-
-		if errors.As(err, &tbErr) {
-			switch tbErr.Category() {
-			case util.CategoryAgent:
-				// MCP - Tool execution error
-				// Return SUCCESS but with IsError: true
-				text := TextContent{
-					Type: "text",
-					Text: err.Error(),
-				}
-				return jsonrpc.JSONRPCResponse{
-					Jsonrpc: jsonrpc.JSONRPC_VERSION,
-					Id:      id,
-					Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
-				}, nil
-
-			case util.CategoryServer:
-				// MCP Spec - Protocol error
-				// Return JSON-RPC ERROR
-				var clientServerErr *util.ClientServerError
-				rpcCode := jsonrpc.INTERNAL_ERROR // Default to Internal Error (-32603)
-
-				if errors.As(err, &clientServerErr) {
-					if clientServerErr.Code == http.StatusUnauthorized || clientServerErr.Code == http.StatusForbidden {
-						if clientAuth {
-							rpcCode = jsonrpc.INVALID_REQUEST
-						} else {
-							rpcCode = jsonrpc.INTERNAL_ERROR
-						}
-					}
-				}
-				return jsonrpc.NewError(id, rpcCode, err.Error(), nil), err
+		errStr := err.Error()
+		// Missing authService tokens.
+		if errors.Is(err, util.ErrUnauthorized) {
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
+		}
+		// Upstream auth error
+		if strings.Contains(errStr, "Error 401") || strings.Contains(errStr, "Error 403") {
+			if clientAuth {
+				// Error with client credentials should pass down to the client
+				return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 			}
-		} else {
-			// Unknown error -> 500
+			// Auth error with ADC should raise internal 500 error
 			return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
 		}
+		text := TextContent{
+			Type: "text",
+			Text: err.Error(),
+		}
+		return jsonrpc.JSONRPCResponse{
+			Jsonrpc: jsonrpc.JSONRPC_VERSION,
+			Id:      id,
+			Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
+		}, nil
 	}
+
 	content := make([]TextContent, 0)
 
 	sliceRes, ok := results.([]any)

internal/server/mcp/v20250618/method.go

@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -116,12 +117,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			errMsg := "missing access token in the 'Authorization' header"
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, errMsg, nil), util.NewClientServerError(
-				errMsg,
-				http.StatusUnauthorized,
-				nil,
-			)
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
 		}
 	}
 
@@ -169,11 +165,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// Check if any of the specified auth services is verified
 	isAuthorized := tool.Authorized(verifiedAuthServices)
 	if !isAuthorized {
-		err = util.NewClientServerError(
-			"unauthorized Tool call: Please make sure you specify correct auth headers",
-			http.StatusUnauthorized,
-			nil,
-		)
+		err = fmt.Errorf("unauthorized Tool call: Please make sure your specify correct auth headers: %w", util.ErrUnauthorized)
 		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
@@ -195,44 +187,29 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// run tool invocation and generate response.
 	results, err := tool.Invoke(ctx, resourceMgr, params, accessToken)
 	if err != nil {
-		var tbErr util.ToolboxError
-
-		if errors.As(err, &tbErr) {
-			switch tbErr.Category() {
-			case util.CategoryAgent:
-				// MCP - Tool execution error
-				// Return SUCCESS but with IsError: true
-				text := TextContent{
-					Type: "text",
-					Text: err.Error(),
-				}
-				return jsonrpc.JSONRPCResponse{
-					Jsonrpc: jsonrpc.JSONRPC_VERSION,
-					Id:      id,
-					Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
-				}, nil
-
-			case util.CategoryServer:
-				// MCP Spec - Protocol error
-				// Return JSON-RPC ERROR
-				var clientServerErr *util.ClientServerError
-				rpcCode := jsonrpc.INTERNAL_ERROR // Default to Internal Error (-32603)
-
-				if errors.As(err, &clientServerErr) {
-					if clientServerErr.Code == http.StatusUnauthorized || clientServerErr.Code == http.StatusForbidden {
-						if clientAuth {
-							rpcCode = jsonrpc.INVALID_REQUEST
-						} else {
-							rpcCode = jsonrpc.INTERNAL_ERROR
-						}
-					}
-				}
-				return jsonrpc.NewError(id, rpcCode, err.Error(), nil), err
+		errStr := err.Error()
+		// Missing authService tokens.
+		if errors.Is(err, util.ErrUnauthorized) {
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
+		}
+		// Upstream auth error
+		if strings.Contains(errStr, "Error 401") || strings.Contains(errStr, "Error 403") {
+			if clientAuth {
+				// Error with client credentials should pass down to the client
+				return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 			}
-		} else {
-			// Unknown error -> 500
+			// Auth error with ADC should raise internal 500 error
 			return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
 		}
+		text := TextContent{
+			Type: "text",
+			Text: err.Error(),
+		}
+		return jsonrpc.JSONRPCResponse{
+			Jsonrpc: jsonrpc.JSONRPC_VERSION,
+			Id:      id,
+			Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
+		}, nil
 	}
 
 	content := make([]TextContent, 0)

internal/server/mcp/v20251125/method.go

@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -116,12 +117,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			errMsg := "missing access token in the 'Authorization' header"
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, errMsg, nil), util.NewClientServerError(
-				errMsg,
-				http.StatusUnauthorized,
-				nil,
-			)
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
 		}
 	}
 
@@ -169,11 +165,7 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// Check if any of the specified auth services is verified
 	isAuthorized := tool.Authorized(verifiedAuthServices)
 	if !isAuthorized {
-		err = util.NewClientServerError(
-			"unauthorized Tool call: Please make sure you specify correct auth headers",
-			http.StatusUnauthorized,
-			nil,
-		)
+		err = fmt.Errorf("unauthorized Tool call: Please make sure your specify correct auth headers: %w", util.ErrUnauthorized)
 		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
@@ -195,44 +187,29 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	// run tool invocation and generate response.
 	results, err := tool.Invoke(ctx, resourceMgr, params, accessToken)
 	if err != nil {
-		var tbErr util.ToolboxError
-
-		if errors.As(err, &tbErr) {
-			switch tbErr.Category() {
-			case util.CategoryAgent:
-				// MCP - Tool execution error
-				// Return SUCCESS but with IsError: true
-				text := TextContent{
-					Type: "text",
-					Text: err.Error(),
-				}
-				return jsonrpc.JSONRPCResponse{
-					Jsonrpc: jsonrpc.JSONRPC_VERSION,
-					Id:      id,
-					Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
-				}, nil
-
-			case util.CategoryServer:
-				// MCP Spec - Protocol error
-				// Return JSON-RPC ERROR
-				var clientServerErr *util.ClientServerError
-				rpcCode := jsonrpc.INTERNAL_ERROR // Default to Internal Error (-32603)
-
-				if errors.As(err, &clientServerErr) {
-					if clientServerErr.Code == http.StatusUnauthorized || clientServerErr.Code == http.StatusForbidden {
-						if clientAuth {
-							rpcCode = jsonrpc.INVALID_REQUEST
-						} else {
-							rpcCode = jsonrpc.INTERNAL_ERROR
-						}
-					}
-				}
-				return jsonrpc.NewError(id, rpcCode, err.Error(), nil), err
+		errStr := err.Error()
+		// Missing authService tokens.
+		if errors.Is(err, util.ErrUnauthorized) {
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
+		}
+		// Upstream auth error
+		if strings.Contains(errStr, "Error 401") || strings.Contains(errStr, "Error 403") {
+			if clientAuth {
+				// Error with client credentials should pass down to the client
+				return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 			}
-		} else {
-			// Unknown error -> 500
+			// Auth error with ADC should raise internal 500 error
 			return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
 		}
+		text := TextContent{
+			Type: "text",
+			Text: err.Error(),
+		}
+		return jsonrpc.JSONRPCResponse{
+			Jsonrpc: jsonrpc.JSONRPC_VERSION,
+			Id:      id,
+			Result:  CallToolResult{Content: []TextContent{text}, IsError: true},
+		}, nil
 	}
 
 	content := make([]TextContent, 0)

internal/server/mcp_test.go

@@ -231,7 +231,7 @@ func TestMcpEndpointWithoutInitialized(t *testing.T) {
 				"id":      "tools-call-tool4",
 				"error": map[string]any{
 					"code":    -32600.0,
-					"message": "unauthorized Tool call: Please make sure you specify correct auth headers: <nil>",
+					"message": "unauthorized Tool call: Please make sure your specify correct auth headers: unauthorized",
 				},
 			},
 		},
@@ -834,7 +834,7 @@ func TestMcpEndpoint(t *testing.T) {
 						"id":      "tools-call-tool4",
 						"error": map[string]any{
 							"code":    -32600.0,
-							"message": "unauthorized Tool call: Please make sure you specify correct auth headers: <nil>",
+							"message": "unauthorized Tool call: Please make sure your specify correct auth headers: unauthorized",
 						},
 					},
 				},

internal/tools/alloydb/alloydbcreatecluster/alloydbcreatecluster.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -123,49 +122,44 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	project, ok := paramsMap["project"].(string)
 	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a non-empty string")
 	}
 
 	location, ok := paramsMap["location"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'location' parameter; expected a string", nil)
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 
 	clusterID, ok := paramsMap["cluster"].(string)
 	if !ok || clusterID == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'cluster' parameter; expected a non-empty string")
 	}
 
 	password, ok := paramsMap["password"].(string)
 	if !ok || password == "" {
-		return nil, util.NewAgentError("invalid or missing 'password' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'password' parameter; expected a non-empty string")
 	}
 
 	network, ok := paramsMap["network"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'network' parameter; expected a string", nil)
+		return nil, fmt.Errorf("invalid 'network' parameter; expected a string")
 	}
 
 	user, ok := paramsMap["user"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'user' parameter; expected a string", nil)
-	}
-	resp, err := source.CreateCluster(ctx, project, location, network, user, password, clusterID, string(accessToken))
-
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("invalid 'user' parameter; expected a string")
 	}
 
-	return resp, nil
+	return source.CreateCluster(ctx, project, location, network, user, password, clusterID, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbcreateinstance/alloydbcreateinstance.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -124,36 +123,36 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	project, ok := paramsMap["project"].(string)
 	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a non-empty string")
 	}
 
 	location, ok := paramsMap["location"].(string)
 	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing 'location' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'location' parameter; expected a non-empty string")
 	}
 
 	cluster, ok := paramsMap["cluster"].(string)
 	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'cluster' parameter; expected a non-empty string")
 	}
 
 	instanceID, ok := paramsMap["instance"].(string)
 	if !ok || instanceID == "" {
-		return nil, util.NewAgentError("invalid or missing 'instance' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'instance' parameter; expected a non-empty string")
 	}
 
 	instanceType, ok := paramsMap["instanceType"].(string)
 	if !ok || (instanceType != "READ_POOL" && instanceType != "PRIMARY") {
-		return nil, util.NewAgentError("invalid 'instanceType' parameter; expected 'PRIMARY' or 'READ_POOL'", nil)
+		return nil, fmt.Errorf("invalid 'instanceType' parameter; expected 'PRIMARY' or 'READ_POOL'")
 	}
 
 	displayName, _ := paramsMap["displayName"].(string)
@@ -162,15 +161,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if instanceType == "READ_POOL" {
 		nodeCount, ok = paramsMap["nodeCount"].(int)
 		if !ok {
-			return nil, util.NewAgentError("invalid 'nodeCount' parameter; expected an integer for READ_POOL", nil)
+			return nil, fmt.Errorf("invalid 'nodeCount' parameter; expected an integer for READ_POOL")
 		}
 	}
 
-	resp, err := source.CreateInstance(ctx, project, location, cluster, instanceID, instanceType, displayName, nodeCount, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateInstance(ctx, project, location, cluster, instanceID, instanceType, displayName, nodeCount, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbcreateuser/alloydbcreateuser.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -123,43 +122,43 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	project, ok := paramsMap["project"].(string)
 	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a non-empty string")
 	}
 
 	location, ok := paramsMap["location"].(string)
 	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing'location' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing'location' parameter; expected a non-empty string")
 	}
 
 	cluster, ok := paramsMap["cluster"].(string)
 	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'cluster' parameter; expected a non-empty string")
 	}
 
 	userID, ok := paramsMap["user"].(string)
 	if !ok || userID == "" {
-		return nil, util.NewAgentError("invalid or missing 'user' parameter; expected a non-empty string", nil)
+		return nil, fmt.Errorf("invalid or missing 'user' parameter; expected a non-empty string")
 	}
 
 	userType, ok := paramsMap["userType"].(string)
 	if !ok || (userType != "ALLOYDB_BUILT_IN" && userType != "ALLOYDB_IAM_USER") {
-		return nil, util.NewAgentError("invalid or missing 'userType' parameter; expected 'ALLOYDB_BUILT_IN' or 'ALLOYDB_IAM_USER'", nil)
+		return nil, fmt.Errorf("invalid or missing 'userType' parameter; expected 'ALLOYDB_BUILT_IN' or 'ALLOYDB_IAM_USER'")
 	}
 	var password string
 
 	if userType == "ALLOYDB_BUILT_IN" {
 		password, ok = paramsMap["password"].(string)
 		if !ok || password == "" {
-			return nil, util.NewAgentError("password is required when userType is ALLOYDB_BUILT_IN", nil)
+			return nil, fmt.Errorf("password is required when userType is ALLOYDB_BUILT_IN")
 		}
 	}
 
@@ -171,11 +170,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 		}
 	}
-	resp, err := source.CreateUser(ctx, userType, password, roles, string(accessToken), project, location, cluster, userID)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateUser(ctx, userType, password, roles, string(accessToken), project, location, cluster, userID)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbgetcluster/alloydbgetcluster.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -121,32 +120,28 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
-	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing 'location' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 	cluster, ok := paramsMap["cluster"].(string)
-	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'cluster' parameter; expected a string")
 	}
 
-	resp, err := source.GetCluster(ctx, project, location, cluster, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetCluster(ctx, project, location, cluster, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbgetinstance/alloydbgetinstance.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -121,36 +120,32 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
-	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing 'location' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 	cluster, ok := paramsMap["cluster"].(string)
-	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'cluster' parameter; expected a string")
 	}
 	instance, ok := paramsMap["instance"].(string)
-	if !ok || instance == "" {
-		return nil, util.NewAgentError("invalid or missing 'instance' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'instance' parameter; expected a string")
 	}
 
-	resp, err := source.GetInstance(ctx, project, location, cluster, instance, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetInstance(ctx, project, location, cluster, instance, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbgetuser/alloydbgetuser.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -121,36 +120,32 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
-	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing 'location' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 	cluster, ok := paramsMap["cluster"].(string)
-	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'cluster' parameter; expected a string")
 	}
 	user, ok := paramsMap["user"].(string)
-	if !ok || user == "" {
-		return nil, util.NewAgentError("invalid or missing 'user' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'user' parameter; expected a string")
 	}
 
-	resp, err := source.GetUsers(ctx, project, location, cluster, user, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetUsers(ctx, project, location, cluster, user, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydblistclusters/alloydblistclusters.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -119,28 +118,24 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'location' parameter; expected a string", nil)
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 
-	resp, err := source.ListCluster(ctx, project, location, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListCluster(ctx, project, location, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydblistinstances/alloydblistinstances.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -120,32 +119,28 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'location' parameter; expected a string", nil)
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 	cluster, ok := paramsMap["cluster"].(string)
 	if !ok {
-		return nil, util.NewAgentError("invalid 'cluster' parameter; expected a string", nil)
+		return nil, fmt.Errorf("invalid 'cluster' parameter; expected a string")
 	}
 
-	resp, err := source.ListInstance(ctx, project, location, cluster, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListInstance(ctx, project, location, cluster, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydblistusers/alloydblistusers.go

@@ -22,7 +22,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -120,32 +119,28 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
-	if !ok || project == "" {
-		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid or missing 'project' parameter; expected a string")
 	}
 	location, ok := paramsMap["location"].(string)
-	if !ok || location == "" {
-		return nil, util.NewAgentError("invalid or missing 'location' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'location' parameter; expected a string")
 	}
 	cluster, ok := paramsMap["cluster"].(string)
-	if !ok || cluster == "" {
-		return nil, util.NewAgentError("invalid or missing 'cluster' parameter; expected a string", nil)
+	if !ok {
+		return nil, fmt.Errorf("invalid 'cluster' parameter; expected a string")
 	}
 
-	resp, err := source.ListUsers(ctx, project, location, cluster, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListUsers(ctx, project, location, cluster, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydb/alloydbwaitforoperation/alloydbwaitforoperation.go

@@ -24,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -214,25 +213,25 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", 500, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	location, ok := paramsMap["location"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'location' parameter", nil)
+		return nil, fmt.Errorf("missing 'location' parameter")
 	}
 	operation, ok := paramsMap["operation"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'operation' parameter", nil)
+		return nil, fmt.Errorf("missing 'operation' parameter")
 	}
 
 	ctx, cancel := context.WithTimeout(ctx, 30*time.Minute)
@@ -247,15 +246,14 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	for retries < maxRetries {
 		select {
 		case <-ctx.Done():
-			return nil, util.NewAgentError("timed out waiting for operation", ctx.Err())
+			return nil, fmt.Errorf("timed out waiting for operation: %w", ctx.Err())
 		default:
 		}
 
 		op, err := source.GetOperations(ctx, project, location, operation, alloyDBConnectionMessageTemplate, delay, string(accessToken))
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
-		}
-		if op != nil {
+			return nil, err
+		} else if op != nil {
 			return op, nil
 		}
 
@@ -266,7 +264,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		}
 		retries++
 	}
-	return nil, util.NewAgentError("exceeded max retries waiting for operation", nil)
+	return nil, fmt.Errorf("exceeded max retries waiting for operation")
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/alloydbainl/alloydbainl.go

@@ -17,14 +17,12 @@ package alloydbainl
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
@@ -129,10 +127,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	sliceParams := params.AsSlice()
@@ -145,7 +143,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	resp, err := source.RunSQL(ctx, t.Statement, allParamValues)
 	if err != nil {
-		return nil, util.NewClientServerError(fmt.Sprintf("error running SQL query: %v. Query: %v , Values: %v. Toolbox v0.19.0+ is only compatible with AlloyDB AI NL v1.0.3+. Please ensure that you are using the latest AlloyDB AI NL extension", err, t.Statement, allParamValues), http.StatusBadRequest, err)
+		return nil, fmt.Errorf("%w. Query: %v , Values: %v. Toolbox v0.19.0+ is only compatible with AlloyDB AI NL v1.0.3+. Please ensure that you are using the latest AlloyDB AI NL extension", err, t.Statement, allParamValues)
 	}
 	return resp, nil
 }

internal/tools/bigquery/bigqueryanalyzecontribution/bigqueryanalyzecontribution.go

@@ -17,7 +17,6 @@ package bigqueryanalyzecontribution
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
@@ -28,7 +27,6 @@ import (
 	bigqueryds "github.com/googleapis/genai-toolbox/internal/sources/bigquery"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 )
@@ -156,21 +154,21 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke runs the contribution analysis.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	inputData, ok := paramsMap["input_data"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast input_data parameter %s", paramsMap["input_data"]), nil)
+		return nil, fmt.Errorf("unable to cast input_data parameter %s", paramsMap["input_data"])
 	}
 
 	bqClient, restService, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	modelID := fmt.Sprintf("contribution_analysis_model_%s", strings.ReplaceAll(uuid.New().String(), "-", ""))
@@ -188,7 +186,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 			options = append(options, fmt.Sprintf("DIMENSION_ID_COLS = [%s]", strings.Join(strCols, ", ")))
 		} else {
-			return nil, util.NewAgentError(fmt.Sprintf("unable to cast dimension_id_cols parameter %s", paramsMap["dimension_id_cols"]), nil)
+			return nil, fmt.Errorf("unable to cast dimension_id_cols parameter %s", paramsMap["dimension_id_cols"])
 		}
 	}
 	if val, ok := paramsMap["top_k_insights_by_apriori_support"]; ok {
@@ -197,7 +195,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := paramsMap["pruning_method"].(string); ok {
 		upperVal := strings.ToUpper(val)
 		if upperVal != "NO_PRUNING" && upperVal != "PRUNE_REDUNDANT_INSIGHTS" {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid pruning_method: %s", val), nil)
+			return nil, fmt.Errorf("invalid pruning_method: %s", val)
 		}
 		options = append(options, fmt.Sprintf("PRUNING_METHOD = '%s'", upperVal))
 	}
@@ -209,7 +207,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			var connProps []*bigqueryapi.ConnectionProperty
 			session, err := source.BigQuerySession()(ctx)
 			if err != nil {
-				return nil, util.NewClientServerError("failed to get BigQuery session", http.StatusInternalServerError, err)
+				return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
 			}
 			if session != nil {
 				connProps = []*bigqueryapi.ConnectionProperty{
@@ -218,22 +216,22 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 			dryRunJob, err := bqutil.DryRunQuery(ctx, restService, source.BigQueryClient().Project(), source.BigQueryClient().Location, inputData, nil, connProps)
 			if err != nil {
-				return nil, util.ProcessGcpError(err)
+				return nil, fmt.Errorf("query validation failed: %w", err)
 			}
 			statementType := dryRunJob.Statistics.Query.StatementType
 			if statementType != "SELECT" {
-				return nil, util.NewAgentError(fmt.Sprintf("the 'input_data' parameter only supports a table ID or a SELECT query. The provided query has statement type '%s'", statementType), nil)
+				return nil, fmt.Errorf("the 'input_data' parameter only supports a table ID or a SELECT query. The provided query has statement type '%s'", statementType)
 			}
 
 			queryStats := dryRunJob.Statistics.Query
 			if queryStats != nil {
 				for _, tableRef := range queryStats.ReferencedTables {
 					if !source.IsDatasetAllowed(tableRef.ProjectId, tableRef.DatasetId) {
-						return nil, util.NewAgentError(fmt.Sprintf("query in input_data accesses dataset '%s.%s', which is not in the allowed list", tableRef.ProjectId, tableRef.DatasetId), nil)
+						return nil, fmt.Errorf("query in input_data accesses dataset '%s.%s', which is not in the allowed list", tableRef.ProjectId, tableRef.DatasetId)
 					}
 				}
 			} else {
-				return nil, util.NewAgentError("could not analyze query in input_data to validate against allowed datasets", nil)
+				return nil, fmt.Errorf("could not analyze query in input_data to validate against allowed datasets")
 			}
 		}
 		inputDataSource = fmt.Sprintf("(%s)", inputData)
@@ -247,10 +245,10 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			case 2: // dataset.table
 				projectID, datasetID = source.BigQueryClient().Project(), parts[0]
 			default:
-				return nil, util.NewAgentError(fmt.Sprintf("invalid table ID format for 'input_data': %q. Expected 'dataset.table' or 'project.dataset.table'", inputData), nil)
+				return nil, fmt.Errorf("invalid table ID format for 'input_data': %q. Expected 'dataset.table' or 'project.dataset.table'", inputData)
 			}
 			if !source.IsDatasetAllowed(projectID, datasetID) {
-				return nil, util.NewAgentError(fmt.Sprintf("access to dataset '%s.%s' (from table '%s') is not allowed", projectID, datasetID, inputData), nil)
+				return nil, fmt.Errorf("access to dataset '%s.%s' (from table '%s') is not allowed", projectID, datasetID, inputData)
 			}
 		}
 		inputDataSource = fmt.Sprintf("SELECT * FROM `%s`", inputData)
@@ -270,7 +268,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Otherwise, a new session will be created by the first query.
 	session, err := source.BigQuerySession()(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to get BigQuery session", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
 	}
 
 	if session != nil {
@@ -283,15 +281,15 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	}
 	createModelJob, err := createModelQuery.Run(ctx)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to start create model job: %w", err)
 	}
 
 	status, err := createModelJob.Wait(ctx)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to wait for create model job: %w", err)
 	}
 	if err := status.Err(); err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("create model job failed: %w", err)
 	}
 
 	// Determine the session ID to use for subsequent queries.
@@ -302,17 +300,12 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	} else if status.Statistics != nil && status.Statistics.SessionInfo != nil {
 		sessionID = status.Statistics.SessionInfo.SessionID
 	} else {
-		return nil, util.NewClientServerError("failed to get or create a BigQuery session ID", http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("failed to get or create a BigQuery session ID")
 	}
 
 	getInsightsSQL := fmt.Sprintf("SELECT * FROM ML.GET_INSIGHTS(MODEL %s)", modelID)
 	connProps := []*bigqueryapi.ConnectionProperty{{Key: "session_id", Value: sessionID}}
-
-	resp, err := source.RunSQL(ctx, bqClient, getInsightsSQL, "SELECT", nil, connProps)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, bqClient, getInsightsSQL, "SELECT", nil, connProps)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/bigquery/bigqueryconversationalanalytics/bigqueryconversationalanalytics.go

@@ -172,10 +172,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	var tokenStr string
@@ -184,26 +184,26 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.UseClientAuthorization() {
 		// Use client-side access token
 		if accessToken == "" {
-			return nil, util.NewClientServerError("tool is configured for client OAuth but no token was provided in the request header", http.StatusUnauthorized, nil)
+			return nil, fmt.Errorf("tool is configured for client OAuth but no token was provided in the request header: %w", util.ErrUnauthorized)
 		}
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	} else {
 		// Get a token source for the Gemini Data Analytics API.
 		tokenSource, err := source.BigQueryTokenSourceWithScope(ctx, nil)
 		if err != nil {
-			return nil, util.NewClientServerError("failed to get token source", http.StatusInternalServerError, err)
+			return nil, fmt.Errorf("failed to get token source: %w", err)
 		}
 
 		// Use cloud-platform token source for Gemini Data Analytics API
 		if tokenSource == nil {
-			return nil, util.NewClientServerError("cloud-platform token source is missing", http.StatusInternalServerError, nil)
+			return nil, fmt.Errorf("cloud-platform token source is missing")
 		}
 		token, err := tokenSource.Token()
 		if err != nil {
-			return nil, util.NewClientServerError("failed to get token from cloud-platform token source", http.StatusInternalServerError, err)
+			return nil, fmt.Errorf("failed to get token from cloud-platform token source: %w", err)
 		}
 		tokenStr = token.AccessToken
 	}
@@ -218,14 +218,14 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	var tableRefs []BQTableReference
 	if tableRefsJSON != "" {
 		if err := json.Unmarshal([]byte(tableRefsJSON), &tableRefs); err != nil {
-			return nil, util.NewAgentError("failed to parse 'table_references' JSON string", err)
+			return nil, fmt.Errorf("failed to parse 'table_references' JSON string: %w", err)
 		}
 	}
 
 	if len(source.BigQueryAllowedDatasets()) > 0 {
 		for _, tableRef := range tableRefs {
 			if !source.IsDatasetAllowed(tableRef.ProjectID, tableRef.DatasetID) {
-				return nil, util.NewAgentError(fmt.Sprintf("access to dataset '%s.%s' (from table '%s') is not allowed", tableRef.ProjectID, tableRef.DatasetID, tableRef.TableID), nil)
+				return nil, fmt.Errorf("access to dataset '%s.%s' (from table '%s') is not allowed", tableRef.ProjectID, tableRef.DatasetID, tableRef.TableID)
 			}
 		}
 	}
@@ -258,8 +258,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Call the streaming API
 	response, err := getStream(caURL, payload, headers, source.GetMaxQueryResultRows())
 	if err != nil {
-		// getStream wraps network errors or non-200 responses
-		return nil, util.NewClientServerError("failed to get response from conversational analytics API", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to get response from conversational analytics API: %w", err)
 	}
 
 	return response, nil

internal/tools/bigquery/bigqueryexecutesql/bigqueryexecutesql.go

@@ -18,7 +18,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net/http"
 	"strings"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
@@ -153,25 +152,25 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	sql, ok := paramsMap["sql"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast sql parameter %s", paramsMap["sql"]), nil)
+		return nil, fmt.Errorf("unable to cast sql parameter %s", paramsMap["sql"])
 	}
 	dryRun, ok := paramsMap["dry_run"].(bool)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast dry_run parameter %s", paramsMap["dry_run"]), nil)
+		return nil, fmt.Errorf("unable to cast dry_run parameter %s", paramsMap["dry_run"])
 	}
 
 	bqClient, restService, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	var connProps []*bigqueryapi.ConnectionProperty
@@ -179,7 +178,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.BigQueryWriteMode() == bigqueryds.WriteModeProtected {
 		session, err = source.BigQuerySession()(ctx)
 		if err != nil {
-			return nil, util.NewClientServerError("failed to get BigQuery session for protected mode", http.StatusInternalServerError, err)
+			return nil, fmt.Errorf("failed to get BigQuery session for protected mode: %w", err)
 		}
 		connProps = []*bigqueryapi.ConnectionProperty{
 			{Key: "session_id", Value: session.ID},
@@ -188,7 +187,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	dryRunJob, err := bqutil.DryRunQuery(ctx, restService, bqClient.Project(), bqClient.Location, sql, nil, connProps)
 	if err != nil {
-		return nil, util.NewClientServerError("query validation failed", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("query validation failed: %w", err)
 	}
 
 	statementType := dryRunJob.Statistics.Query.StatementType
@@ -196,13 +195,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	switch source.BigQueryWriteMode() {
 	case bigqueryds.WriteModeBlocked:
 		if statementType != "SELECT" {
-			return nil, util.NewAgentError("write mode is 'blocked', only SELECT statements are allowed", nil)
+			return nil, fmt.Errorf("write mode is 'blocked', only SELECT statements are allowed")
 		}
 	case bigqueryds.WriteModeProtected:
 		if dryRunJob.Configuration != nil && dryRunJob.Configuration.Query != nil {
 			if dest := dryRunJob.Configuration.Query.DestinationTable; dest != nil && dest.DatasetId != session.DatasetID {
-				return nil, util.NewAgentError(fmt.Sprintf("protected write mode only supports SELECT statements, or write operations in the anonymous "+
-					"dataset of a BigQuery session, but destination was %q", dest.DatasetId), nil)
+				return nil, fmt.Errorf("protected write mode only supports SELECT statements, or write operations in the anonymous "+
+					"dataset of a BigQuery session, but destination was %q", dest.DatasetId)
 			}
 		}
 	}
@@ -210,11 +209,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if len(source.BigQueryAllowedDatasets()) > 0 {
 		switch statementType {
 		case "CREATE_SCHEMA", "DROP_SCHEMA", "ALTER_SCHEMA":
-			return nil, util.NewAgentError(fmt.Sprintf("dataset-level operations like '%s' are not allowed when dataset restrictions are in place", statementType), nil)
+			return nil, fmt.Errorf("dataset-level operations like '%s' are not allowed when dataset restrictions are in place", statementType)
 		case "CREATE_FUNCTION", "CREATE_TABLE_FUNCTION", "CREATE_PROCEDURE":
-			return nil, util.NewAgentError(fmt.Sprintf("creating stored routines ('%s') is not allowed when dataset restrictions are in place, as their contents cannot be safely analyzed", statementType), nil)
+			return nil, fmt.Errorf("creating stored routines ('%s') is not allowed when dataset restrictions are in place, as their contents cannot be safely analyzed", statementType)
 		case "CALL":
-			return nil, util.NewAgentError(fmt.Sprintf("calling stored procedures ('%s') is not allowed when dataset restrictions are in place, as their contents cannot be safely analyzed", statementType), nil)
+			return nil, fmt.Errorf("calling stored procedures ('%s') is not allowed when dataset restrictions are in place, as their contents cannot be safely analyzed", statementType)
 		}
 
 		// Use a map to avoid duplicate table names.
@@ -245,7 +244,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			parsedTables, parseErr := bqutil.TableParser(sql, source.BigQueryClient().Project())
 			if parseErr != nil {
 				// If parsing fails (e.g., EXECUTE IMMEDIATE), we cannot guarantee safety, so we must fail.
-				return nil, util.NewAgentError("could not parse tables from query to validate against allowed datasets", parseErr)
+				return nil, fmt.Errorf("could not parse tables from query to validate against allowed datasets: %w", parseErr)
 			}
 			tableNames = parsedTables
 		}
@@ -255,7 +254,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			if len(parts) == 3 {
 				projectID, datasetID := parts[0], parts[1]
 				if !source.IsDatasetAllowed(projectID, datasetID) {
-					return nil, util.NewAgentError(fmt.Sprintf("query accesses dataset '%s.%s', which is not in the allowed list", projectID, datasetID), nil)
+					return nil, fmt.Errorf("query accesses dataset '%s.%s', which is not in the allowed list", projectID, datasetID)
 				}
 			}
 		}
@@ -265,7 +264,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		if dryRunJob != nil {
 			jobJSON, err := json.MarshalIndent(dryRunJob, "", "  ")
 			if err != nil {
-				return nil, util.NewClientServerError("failed to marshal dry run job to JSON", http.StatusInternalServerError, err)
+				return nil, fmt.Errorf("failed to marshal dry run job to JSON: %w", err)
 			}
 			return string(jobJSON), nil
 		}
@@ -276,14 +275,10 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Log the query executed for debugging.
 	logger, err := util.LoggerFromContext(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("error getting logger", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting logger: %s", err)
 	}
 	logger.DebugContext(ctx, fmt.Sprintf("executing `%s` tool query: %s", resourceType, sql))
-	resp, err := source.RunSQL(ctx, bqClient, sql, statementType, nil, connProps)
-	if err != nil {
-		return nil, util.NewClientServerError("error running sql", http.StatusInternalServerError, err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, bqClient, sql, statementType, nil, connProps)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/bigquery/bigqueryforecast/bigqueryforecast.go

@@ -17,7 +17,6 @@ package bigqueryforecast
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
@@ -134,34 +133,34 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	historyData, ok := paramsMap["history_data"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast history_data parameter %v", paramsMap["history_data"]), nil)
+		return nil, fmt.Errorf("unable to cast history_data parameter %v", paramsMap["history_data"])
 	}
 	timestampCol, ok := paramsMap["timestamp_col"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast timestamp_col parameter %v", paramsMap["timestamp_col"]), nil)
+		return nil, fmt.Errorf("unable to cast timestamp_col parameter %v", paramsMap["timestamp_col"])
 	}
 	dataCol, ok := paramsMap["data_col"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast data_col parameter %v", paramsMap["data_col"]), nil)
+		return nil, fmt.Errorf("unable to cast data_col parameter %v", paramsMap["data_col"])
 	}
 	idColsRaw, ok := paramsMap["id_cols"].([]any)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast id_cols parameter %v", paramsMap["id_cols"]), nil)
+		return nil, fmt.Errorf("unable to cast id_cols parameter %v", paramsMap["id_cols"])
 	}
 	var idCols []string
 	for _, v := range idColsRaw {
 		s, ok := v.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("id_cols contains non-string value: %v", v), nil)
+			return nil, fmt.Errorf("id_cols contains non-string value: %v", v)
 		}
 		idCols = append(idCols, s)
 	}
@@ -170,13 +169,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		if h, ok := paramsMap["horizon"].(float64); ok {
 			horizon = int(h)
 		} else {
-			return nil, util.NewAgentError(fmt.Sprintf("unable to cast horizon parameter %v", paramsMap["horizon"]), nil)
+			return nil, fmt.Errorf("unable to cast horizon parameter %v", paramsMap["horizon"])
 		}
 	}
 
 	bqClient, restService, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	var historyDataSource string
@@ -186,7 +185,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			var connProps []*bigqueryapi.ConnectionProperty
 			session, err := source.BigQuerySession()(ctx)
 			if err != nil {
-				return nil, util.NewClientServerError("failed to get BigQuery session", http.StatusInternalServerError, err)
+				return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
 			}
 			if session != nil {
 				connProps = []*bigqueryapi.ConnectionProperty{
@@ -195,22 +194,22 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 			dryRunJob, err := bqutil.DryRunQuery(ctx, restService, source.BigQueryClient().Project(), source.BigQueryClient().Location, historyData, nil, connProps)
 			if err != nil {
-				return nil, util.ProcessGcpError(err)
+				return nil, fmt.Errorf("query validation failed: %w", err)
 			}
 			statementType := dryRunJob.Statistics.Query.StatementType
 			if statementType != "SELECT" {
-				return nil, util.NewAgentError(fmt.Sprintf("the 'history_data' parameter only supports a table ID or a SELECT query. The provided query has statement type '%s'", statementType), nil)
+				return nil, fmt.Errorf("the 'history_data' parameter only supports a table ID or a SELECT query. The provided query has statement type '%s'", statementType)
 			}
 
 			queryStats := dryRunJob.Statistics.Query
 			if queryStats != nil {
 				for _, tableRef := range queryStats.ReferencedTables {
 					if !source.IsDatasetAllowed(tableRef.ProjectId, tableRef.DatasetId) {
-						return nil, util.NewAgentError(fmt.Sprintf("query in history_data accesses dataset '%s.%s', which is not in the allowed list", tableRef.ProjectId, tableRef.DatasetId), nil)
+						return nil, fmt.Errorf("query in history_data accesses dataset '%s.%s', which is not in the allowed list", tableRef.ProjectId, tableRef.DatasetId)
 					}
 				}
 			} else {
-				return nil, util.NewAgentError("could not analyze query in history_data to validate against allowed datasets", nil)
+				return nil, fmt.Errorf("could not analyze query in history_data to validate against allowed datasets")
 			}
 		}
 		historyDataSource = fmt.Sprintf("(%s)", historyData)
@@ -227,11 +226,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 				projectID = source.BigQueryClient().Project()
 				datasetID = parts[0]
 			default:
-				return nil, util.NewAgentError(fmt.Sprintf("invalid table ID format for 'history_data': %q. Expected 'dataset.table' or 'project.dataset.table'", historyData), nil)
+				return nil, fmt.Errorf("invalid table ID format for 'history_data': %q. Expected 'dataset.table' or 'project.dataset.table'", historyData)
 			}
 
 			if !source.IsDatasetAllowed(projectID, datasetID) {
-				return nil, util.NewAgentError(fmt.Sprintf("access to dataset '%s.%s' (from table '%s') is not allowed", projectID, datasetID, historyData), nil)
+				return nil, fmt.Errorf("access to dataset '%s.%s' (from table '%s') is not allowed", projectID, datasetID, historyData)
 			}
 		}
 		historyDataSource = fmt.Sprintf("TABLE `%s`", historyData)
@@ -244,15 +243,15 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	}
 	sql := fmt.Sprintf(`SELECT * 
 		FROM AI.FORECAST(
-            %s,
-            data_col => '%s',
-            timestamp_col => '%s',
-            horizon => %d%s)`,
+			%s,
+			data_col => '%s',
+			timestamp_col => '%s',
+			horizon => %d%s)`,
 		historyDataSource, dataCol, timestampCol, horizon, idColsArg)
 
 	session, err := source.BigQuerySession()(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to get BigQuery session", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
 	}
 	var connProps []*bigqueryapi.ConnectionProperty
 	if session != nil {
@@ -265,15 +264,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Log the query executed for debugging.
 	logger, err := util.LoggerFromContext(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("error getting logger", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting logger: %s", err)
 	}
 	logger.DebugContext(ctx, fmt.Sprintf("executing `%s` tool query: %s", resourceType, sql))
 
-	resp, err := source.RunSQL(ctx, bqClient, sql, "SELECT", nil, connProps)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, bqClient, sql, "SELECT", nil, connProps)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/bigquery/bigquerygetdatasetinfo/bigquerygetdatasetinfo.go

@@ -17,7 +17,6 @@ package bigquerygetdatasetinfo
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
 	yaml "github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 )
@@ -122,38 +120,38 @@ type Tool struct {
 func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	projectId, ok := mapParams[projectKey].(string)
 	if !ok {
-		// Updated: Use fmt.Sprintf for formatting, pass nil as cause
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", projectKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", projectKey)
 	}
 
 	datasetId, ok := mapParams[datasetKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", datasetKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", datasetKey)
 	}
 
 	bqClient, _, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	if !source.IsDatasetAllowed(projectId, datasetId) {
-		return nil, util.NewClientServerError(fmt.Sprintf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId), http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId)
 	}
 
 	dsHandle := bqClient.DatasetInProject(projectId, datasetId)
 
 	metadata, err := dsHandle.Metadata(ctx)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to get metadata for dataset %s (in project %s): %w", datasetId, projectId, err)
 	}
 
 	return metadata, nil

internal/tools/bigquery/bigquerygettableinfo/bigquerygettableinfo.go

@@ -17,7 +17,6 @@ package bigquerygettableinfo
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
 	yaml "github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 )
@@ -127,35 +125,35 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	projectId, ok := mapParams[projectKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", projectKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", projectKey)
 	}
 
 	datasetId, ok := mapParams[datasetKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", datasetKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", datasetKey)
 	}
 
 	tableId, ok := mapParams[tableKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", tableKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", tableKey)
 	}
 
 	if !source.IsDatasetAllowed(projectId, datasetId) {
-		return nil, util.NewClientServerError(fmt.Sprintf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId), http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId)
 	}
 
 	bqClient, _, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	dsHandle := bqClient.DatasetInProject(projectId, datasetId)
@@ -163,7 +161,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	metadata, err := tableHandle.Metadata(ctx)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to get metadata for table %s.%s.%s: %w", projectId, datasetId, tableId, err)
 	}
 
 	return metadata, nil

internal/tools/bigquery/bigquerylistdatasetids/bigquerylistdatasetids.go

@@ -17,14 +17,12 @@ package bigquerylistdatasetids
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 	"google.golang.org/api/iterator"
@@ -122,10 +120,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	if len(source.BigQueryAllowedDatasets()) > 0 {
@@ -134,12 +132,12 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	mapParams := params.AsMap()
 	projectId, ok := mapParams[projectKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", projectKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", projectKey)
 	}
 
 	bqClient, _, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	datasetIterator := bqClient.Datasets(ctx)
 	datasetIterator.ProjectID = projectId
@@ -151,7 +149,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			break
 		}
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
+			return nil, fmt.Errorf("unable to iterate through datasets: %w", err)
 		}
 
 		// Remove leading and trailing quotes

internal/tools/bigquery/bigquerylisttableids/bigquerylisttableids.go

@@ -17,7 +17,6 @@ package bigquerylisttableids
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	bigqueryapi "cloud.google.com/go/bigquery"
 	yaml "github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 	"google.golang.org/api/iterator"
@@ -125,30 +123,31 @@ type Tool struct {
 func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	projectId, ok := mapParams[projectKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", projectKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", projectKey)
 	}
 
 	datasetId, ok := mapParams[datasetKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", datasetKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", datasetKey)
 	}
 
 	if !source.IsDatasetAllowed(projectId, datasetId) {
-		return nil, util.NewClientServerError(fmt.Sprintf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId), http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("access denied to dataset '%s' because it is not in the configured list of allowed datasets for project '%s'", datasetId, projectId)
 	}
 
 	bqClient, _, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	dsHandle := bqClient.DatasetInProject(projectId, datasetId)
@@ -161,7 +160,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			break
 		}
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
+			return nil, fmt.Errorf("failed to iterate through tables in dataset %s.%s: %w", projectId, datasetId, err)
 		}
 
 		// Remove leading and trailing quotes

internal/tools/bigquery/bigquerysearchcatalog/bigquerysearchcatalog.go

@@ -17,7 +17,6 @@ package bigquerysearchcatalog
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	dataplexapi "cloud.google.com/go/dataplex/apiv1"
@@ -27,7 +26,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	bigqueryds "github.com/googleapis/genai-toolbox/internal/sources/bigquery"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/iterator"
 )
@@ -188,31 +186,28 @@ func ExtractType(resourceString string) string {
 	return typeMap[resourceString[lastIndex+1:]]
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	pageSize := int32(paramsMap["pageSize"].(int))
 	prompt, _ := paramsMap["prompt"].(string)
-
 	projectIdSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["projectIds"].([]any), "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("can't convert projectIds to array of strings: %s", err), err)
+		return nil, fmt.Errorf("can't convert projectIds to array of strings: %s", err)
 	}
 	projectIds := projectIdSlice.([]string)
-
 	datasetIdSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["datasetIds"].([]any), "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("can't convert datasetIds to array of strings: %s", err), err)
+		return nil, fmt.Errorf("can't convert datasetIds to array of strings: %s", err)
 	}
 	datasetIds := datasetIdSlice.([]string)
-
 	typesSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["types"].([]any), "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("can't convert types to array of strings: %s", err), err)
+		return nil, fmt.Errorf("can't convert types to array of strings: %s", err)
 	}
 	types := typesSlice.([]string)
 
@@ -228,17 +223,17 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.UseClientAuthorization() {
 		tokenStr, err := accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 		catalogClient, err = dataplexClientCreator(tokenStr)
 		if err != nil {
-			return nil, util.NewClientServerError("error creating client from OAuth access token", http.StatusInternalServerError, err)
+			return nil, fmt.Errorf("error creating client from OAuth access token: %w", err)
 		}
 	}
 
 	it := catalogClient.SearchEntries(ctx, req)
 	if it == nil {
-		return nil, util.NewClientServerError(fmt.Sprintf("failed to create search entries iterator for project %q", source.BigQueryProject()), http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("failed to create search entries iterator for project %q", source.BigQueryProject())
 	}
 
 	var results []Response
@@ -248,7 +243,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			break
 		}
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
+			break
 		}
 		entrySource := entry.DataplexEntry.GetEntrySource()
 		resp := Response{

internal/tools/bigquery/bigquerysql/bigquerysql.go

@@ -17,7 +17,6 @@ package bigquerysql
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"reflect"
 	"strings"
 
@@ -28,7 +27,6 @@ import (
 	bigqueryds "github.com/googleapis/genai-toolbox/internal/sources/bigquery"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	bigqueryrestapi "google.golang.org/api/bigquery/v2"
 )
@@ -105,10 +103,11 @@ type Tool struct {
 func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	highLevelParams := make([]bigqueryapi.QueryParameter, 0, len(t.Parameters))
@@ -117,7 +116,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	paramsMap := params.AsMap()
 	newStatement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params %w", err)
 	}
 
 	for _, p := range t.Parameters {
@@ -128,13 +127,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		if arrayParam, ok := p.(*parameters.ArrayParameter); ok {
 			arrayParamValue, ok := value.([]any)
 			if !ok {
-				return nil, util.NewAgentError(fmt.Sprintf("unable to convert parameter `%s` to []any", name), nil)
+				return nil, fmt.Errorf("unable to convert parameter `%s` to []any", name)
 			}
 			itemType := arrayParam.GetItems().GetType()
 			var err error
 			value, err = parameters.ConvertAnySliceToTyped(arrayParamValue, itemType)
 			if err != nil {
-				return nil, util.NewAgentError(fmt.Sprintf("unable to convert parameter `%s` from []any to typed slice", name), err)
+				return nil, fmt.Errorf("unable to convert parameter `%s` from []any to typed slice: %w", name, err)
 			}
 		}
 
@@ -162,7 +161,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			lowLevelParam.ParameterType.Type = "ARRAY"
 			itemType, err := bqutil.BQTypeStringFromToolType(arrayParam.GetItems().GetType())
 			if err != nil {
-				return nil, util.NewAgentError("unable to get BigQuery type from tool parameter type", err)
+				return nil, err
 			}
 			lowLevelParam.ParameterType.ArrayType = &bigqueryrestapi.QueryParameterType{Type: itemType}
 
@@ -179,7 +178,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			// Handle scalar types based on their defined type.
 			bqType, err := bqutil.BQTypeStringFromToolType(p.GetType())
 			if err != nil {
-				return nil, util.NewAgentError("unable to get BigQuery type from tool parameter type", err)
+				return nil, err
 			}
 			lowLevelParam.ParameterType.Type = bqType
 			lowLevelParam.ParameterValue.Value = fmt.Sprintf("%v", value)
@@ -191,7 +190,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.BigQuerySession() != nil {
 		session, err := source.BigQuerySession()(ctx)
 		if err != nil {
-			return nil, util.NewClientServerError("failed to get BigQuery session", http.StatusInternalServerError, err)
+			return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
 		}
 		if session != nil {
 			// Add session ID to the connection properties for subsequent calls.
@@ -201,20 +200,17 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	bqClient, restService, err := source.RetrieveClientAndService(accessToken)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to retrieve BigQuery client", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	dryRunJob, err := bqutil.DryRunQuery(ctx, restService, bqClient.Project(), bqClient.Location, newStatement, lowLevelParams, connProps)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("query validation failed: %w", err)
 	}
 
 	statementType := dryRunJob.Statistics.Query.StatementType
-	resp, err := source.RunSQL(ctx, bqClient, newStatement, statementType, highLevelParams, connProps)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+
+	return source.RunSQL(ctx, bqClient, newStatement, statementType, highLevelParams, connProps)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/bigtable/bigtable.go

@@ -17,14 +17,12 @@ package bigtable
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"cloud.google.com/go/bigtable"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -98,28 +96,24 @@ type Tool struct {
 func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	newStatement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params %w", err)
 	}
 
 	newParams, err := parameters.GetParams(t.Parameters, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract standard params", err)
+		return nil, fmt.Errorf("unable to extract standard params %w", err)
 	}
-
-	resp, err := source.RunSQL(ctx, newStatement, t.Parameters, newParams)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, newStatement, t.Parameters, newParams)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cassandra/cassandracql/cassandracql.go

@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//  http://www.apache.org/licenses/LICENSE-2.0
+//	http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ -17,14 +17,12 @@ package cassandracql
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	gocql "github.com/apache/cassandra-gocql-driver/v2"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -109,27 +107,23 @@ func (t Tool) Authorized(verifiedAuthServices []string) bool {
 }
 
 // Invoke implements tools.Tool.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	newStatement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params %w", err)
 	}
 
 	newParams, err := parameters.GetParams(t.Parameters, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract standard params", err)
+		return nil, fmt.Errorf("unable to extract standard params %w", err)
 	}
-	resp, err := source.RunSQL(ctx, newStatement, newParams)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, newStatement, newParams)
 }
 
 // Manifest implements tools.Tool.

internal/tools/clickhouse/clickhouseexecutesql/clickhouseexecutesql.go

@@ -17,13 +17,11 @@ package clickhouse
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -89,22 +87,18 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	sql, ok := paramsMap["sql"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast sql parameter %s", paramsMap["sql"]), nil)
+		return nil, fmt.Errorf("unable to cast sql parameter %s", paramsMap["sql"])
 	}
-	resp, err := source.RunSQL(ctx, sql, nil)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, sql, nil)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/clickhouse/clickhouselistdatabases/clickhouselistdatabases.go

@@ -17,13 +17,11 @@ package clickhouse
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -88,10 +86,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	// Query to list all databases
@@ -99,7 +97,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	out, err := source.RunSQL(ctx, query, nil)
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, err
 	}
 
 	return out, nil

internal/tools/clickhouse/clickhouselisttables/clickhouselisttables.go

@@ -17,13 +17,11 @@ package clickhouse
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -92,37 +90,34 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	database, ok := mapParams[databaseKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", databaseKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", databaseKey)
 	}
-
 	// Query to list all tables in the specified database
-	// Note: formatting identifier directly is risky if input is untrusted, but standard for this tool structure.
 	query := fmt.Sprintf("SHOW TABLES FROM %s", database)
 
 	out, err := source.RunSQL(ctx, query, nil)
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, err
 	}
 
 	res, ok := out.([]any)
 	if !ok {
-		return nil, util.NewClientServerError("unable to convert result to list", http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("unable to convert result to list")
 	}
-
 	var tables []map[string]any
 	for _, item := range res {
 		tableMap, ok := item.(map[string]any)
 		if !ok {
-			return nil, util.NewClientServerError(fmt.Sprintf("unexpected type in result: got %T, want map[string]any", item), http.StatusInternalServerError, nil)
+			return nil, fmt.Errorf("unexpected type in result: got %T, want map[string]any", item)
 		}
 		tableMap["database"] = database
 		tables = append(tables, tableMap)

internal/tools/clickhouse/clickhousesql/clickhousesql.go

@@ -17,13 +17,11 @@ package clickhouse
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -90,28 +88,24 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, token tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	newStatement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params: %w", err)
 	}
 
 	newParams, err := parameters.GetParams(t.Parameters, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract standard params", err)
+		return nil, fmt.Errorf("unable to extract standard params: %w", err)
 	}
 
-	resp, err := source.RunSQL(ctx, newStatement, newParams)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, newStatement, newParams)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudgda/cloudgda.go

@@ -18,13 +18,11 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -121,16 +119,17 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+// Invoke executes the tool logic
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	query, ok := paramsMap["query"].(string)
 	if !ok {
-		return nil, util.NewAgentError("query parameter not found or not a string", nil)
+		return nil, fmt.Errorf("query parameter not found or not a string")
 	}
 
 	// Parse the access token if provided
@@ -139,7 +138,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		var err error
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 
@@ -155,14 +154,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	bodyBytes, err := json.Marshal(payload)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to marshal request payload", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to marshal request payload: %w", err)
 	}
-
-	resp, err := source.RunQuery(ctx, tokenStr, bodyBytes)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RunQuery(ctx, tokenStr, bodyBytes)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcarefhirfetchpage/cloudhealthcarefhirfetchpage.go

@@ -17,13 +17,11 @@ package fhirfetchpage
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -95,31 +93,24 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	url, ok := params.AsMap()[pageURLKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", pageURLKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", pageURLKey)
 	}
-
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-
-	resp, err := source.FHIRFetchPage(ctx, url, tokenStr)
-	if err != nil {
-
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.FHIRFetchPage(ctx, url, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcarefhirpatienteverything/cloudhealthcarefhirpatienteverything.go

@@ -17,7 +17,6 @@ package fhirpatienteverything
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	"github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/googleapi"
 )
@@ -118,27 +116,26 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
 	if err != nil {
-		// ValidateAndFetchStoreID usually returns input validation errors
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	patientID, ok := params.AsMap()[patientIDKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", patientIDKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", patientIDKey)
 	}
 
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 
@@ -146,11 +143,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := params.AsMap()[typeFilterKey]; ok {
 		types, ok := val.([]any)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string array", typeFilterKey), nil)
+			return nil, fmt.Errorf("invalid '%s' parameter; expected a string array", typeFilterKey)
 		}
 		typeFilterSlice, err := parameters.ConvertAnySliceToTyped(types, "string")
 		if err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("can't convert '%s' to array of strings: %s", typeFilterKey, err), err)
+			return nil, fmt.Errorf("can't convert '%s' to array of strings: %s", typeFilterKey, err)
 		}
 		if len(typeFilterSlice.([]string)) != 0 {
 			opts = append(opts, googleapi.QueryParameter("_type", strings.Join(typeFilterSlice.([]string), ",")))
@@ -159,18 +156,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if since, ok := params.AsMap()[sinceFilterKey]; ok {
 		sinceStr, ok := since.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", sinceFilterKey), nil)
+			return nil, fmt.Errorf("invalid '%s' parameter; expected a string", sinceFilterKey)
 		}
 		if sinceStr != "" {
 			opts = append(opts, googleapi.QueryParameter("_since", sinceStr))
 		}
 	}
-
-	resp, err := source.FHIRPatientEverything(storeID, patientID, tokenStr, opts)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.FHIRPatientEverything(storeID, patientID, tokenStr, opts)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcarefhirpatientsearch/cloudhealthcarefhirpatientsearch.go

@@ -17,7 +17,6 @@ package fhirpatientsearch
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	"github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/googleapi"
 )
@@ -152,22 +150,22 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 
@@ -181,14 +179,14 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			var ok bool
 			summary, ok = v.(bool)
 			if !ok {
-				return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a boolean", summaryKey), nil)
+				return nil, fmt.Errorf("invalid '%s' parameter; expected a boolean", summaryKey)
 			}
 			continue
 		}
 
 		val, ok := v.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid parameter '%s'; expected a string", k), nil)
+			return nil, fmt.Errorf("invalid parameter '%s'; expected a string", k)
 		}
 		if val == "" {
 			continue
@@ -207,7 +205,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 			parts := strings.Split(val, "/")
 			if len(parts) != 2 {
-				return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' format; expected YYYY-MM-DD/YYYY-MM-DD", k), nil)
+				return nil, fmt.Errorf("invalid '%s' format; expected YYYY-MM-DD/YYYY-MM-DD", k)
 			}
 			var values []string
 			if parts[0] != "" {
@@ -231,17 +229,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		case familyNameKey:
 			opts = append(opts, googleapi.QueryParameter("family", val))
 		default:
-			return nil, util.NewAgentError(fmt.Sprintf("unexpected parameter key %q", k), nil)
+			return nil, fmt.Errorf("unexpected parameter key %q", k)
 		}
 	}
 	if summary {
 		opts = append(opts, googleapi.QueryParameter("_summary", "text"))
 	}
-	resp, err := source.FHIRPatientSearch(storeID, tokenStr, opts)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.FHIRPatientSearch(storeID, tokenStr, opts)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetdataset/cloudhealthcaregetdataset.go

@@ -17,13 +17,11 @@ package gethealthcaredataset
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -92,23 +90,19 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetDataset(tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetDataset(tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetdicomstore/cloudhealthcaregetdicomstore.go

@@ -17,14 +17,12 @@ package getdicomstore
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -109,27 +107,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetDICOMStore(storeID, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetDICOMStore(storeID, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetdicomstoremetrics/cloudhealthcaregetdicomstoremetrics.go

@@ -17,14 +17,12 @@ package getdicomstoremetrics
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -109,27 +107,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetDICOMStoreMetrics(storeID, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetDICOMStoreMetrics(storeID, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetfhirresource/cloudhealthcaregetfhirresource.go

@@ -17,14 +17,12 @@ package getfhirresource
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -114,36 +112,32 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	resType, ok := params.AsMap()[typeKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", typeKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", typeKey)
 	}
 	resID, ok := params.AsMap()[idKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", idKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected a string", idKey)
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetFHIRResource(storeID, resType, resID, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetFHIRResource(storeID, resType, resID, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetfhirstore/cloudhealthcaregetfhirstore.go

@@ -17,14 +17,12 @@ package getfhirstore
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -109,27 +107,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetFHIRStore(storeID, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetFHIRStore(storeID, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaregetfhirstoremetrics/cloudhealthcaregetfhirstoremetrics.go

@@ -17,14 +17,12 @@ package getfhirstoremetrics
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -109,27 +107,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.GetFHIRStoreMetrics(storeID, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetFHIRStoreMetrics(storeID, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcarelistdicomstores/cloudhealthcarelistdicomstores.go

@@ -17,13 +17,11 @@ package listdicomstores
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -92,23 +90,19 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.ListDICOMStores(tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListDICOMStores(tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcarelistfhirstores/cloudhealthcarelistfhirstores.go

@@ -17,13 +17,11 @@ package listfhirstores
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/healthcare/v1"
 )
@@ -92,23 +90,19 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
-	resp, err := source.ListFHIRStores(tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListFHIRStores(tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcareretrieverendereddicominstance/cloudhealthcareretrieverendereddicominstance.go

@@ -17,14 +17,12 @@ package retrieverendereddicominstance
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -119,44 +117,40 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 	study, ok := params.AsMap()[studyInstanceUIDKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", studyInstanceUIDKey), nil)
+		return nil, fmt.Errorf("invalid '%s' parameter; expected a string", studyInstanceUIDKey)
 	}
 	series, ok := params.AsMap()[seriesInstanceUIDKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", seriesInstanceUIDKey), nil)
+		return nil, fmt.Errorf("invalid '%s' parameter; expected a string", seriesInstanceUIDKey)
 	}
 	sop, ok := params.AsMap()[sopInstanceUIDKey].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", sopInstanceUIDKey), nil)
+		return nil, fmt.Errorf("invalid '%s' parameter; expected a string", sopInstanceUIDKey)
 	}
 	frame, ok := params.AsMap()[frameNumberKey].(int)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected an integer", frameNumberKey), nil)
+		return nil, fmt.Errorf("invalid '%s' parameter; expected an integer", frameNumberKey)
 	}
-	resp, err := source.RetrieveRenderedDICOMInstance(storeID, study, series, sop, frame, tokenStr)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RetrieveRenderedDICOMInstance(storeID, study, series, sop, frame, tokenStr)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaresearchdicominstances/cloudhealthcaresearchdicominstances.go

@@ -17,7 +17,6 @@ package searchdicominstances
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	"github.com/goccy/go-yaml"
@@ -25,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/googleapi"
 )
@@ -133,33 +131,33 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 
 	opts, err := common.ParseDICOMSearchParameters(params, []string{sopInstanceUIDKey, patientNameKey, patientIDKey, accessionNumberKey, referringPhysicianNameKey, studyDateKey, modalityKey})
 	if err != nil {
-		return nil, util.NewAgentError("failed to parse DICOM search parameters", err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 	dicomWebPath := "instances"
 	if studyInstanceUID, ok := paramsMap[studyInstanceUIDKey]; ok {
 		id, ok := studyInstanceUID.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", studyInstanceUIDKey), nil)
+			return nil, fmt.Errorf("invalid '%s' parameter; expected a string", studyInstanceUIDKey)
 		}
 		if id != "" {
 			dicomWebPath = fmt.Sprintf("studies/%s/instances", id)
@@ -168,7 +166,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if seriesInstanceUID, ok := paramsMap[seriesInstanceUIDKey]; ok {
 		id, ok := seriesInstanceUID.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", seriesInstanceUIDKey), nil)
+			return nil, fmt.Errorf("invalid '%s' parameter; expected a string", seriesInstanceUIDKey)
 		}
 		if id != "" {
 			if dicomWebPath != "instances" {
@@ -178,11 +176,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			}
 		}
 	}
-	resp, err := source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaresearchdicomseries/cloudhealthcaresearchdicomseries.go

@@ -17,14 +17,12 @@ package searchdicomseries
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/googleapi"
 )
@@ -130,44 +128,40 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 
 	opts, err := common.ParseDICOMSearchParameters(params, []string{seriesInstanceUIDKey, patientNameKey, patientIDKey, accessionNumberKey, referringPhysicianNameKey, studyDateKey, modalityKey})
 	if err != nil {
-		return nil, util.NewAgentError("failed to parse DICOM search parameters", err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 	dicomWebPath := "series"
 	if studyInstanceUID, ok := paramsMap[studyInstanceUIDKey]; ok {
 		id, ok := studyInstanceUID.(string)
 		if !ok {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid '%s' parameter; expected a string", studyInstanceUIDKey), nil)
+			return nil, fmt.Errorf("invalid '%s' parameter; expected a string", studyInstanceUIDKey)
 		}
 		if id != "" {
 			dicomWebPath = fmt.Sprintf("studies/%s/series", id)
 		}
 	}
-	resp, err := source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudhealthcare/cloudhealthcaresearchdicomstudies/cloudhealthcaresearchdicomstudies.go

@@ -17,14 +17,12 @@ package searchdicomstudies
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/common"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/googleapi"
 )
@@ -126,32 +124,28 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedDICOMStores())
 	if err != nil {
-		return nil, util.NewAgentError("failed to validate store ID", err)
+		return nil, err
 	}
 	var tokenStr string
 	if source.UseClientAuthorization() {
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("error parsing access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("error parsing access token: %w", err)
 		}
 	}
 	opts, err := common.ParseDICOMSearchParameters(params, []string{studyInstanceUIDKey, patientNameKey, patientIDKey, accessionNumberKey, referringPhysicianNameKey, studyDateKey})
 	if err != nil {
-		return nil, util.NewAgentError("failed to parse DICOM search parameters", err)
+		return nil, err
 	}
 	dicomWebPath := "studies"
-	resp, err := source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.SearchDICOM(t.Type, storeID, dicomWebPath, tokenStr, opts)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudloggingadmin/cloudloggingadminlistlognames/cloudloggingadminlistlognames.go

@@ -16,13 +16,11 @@ package cloudloggingadminlistlognames
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -91,10 +89,10 @@ type Tool struct {
 	Parameters  parameters.Parameters `yaml:"parameters"`
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	limit := defaultLimit
@@ -102,22 +100,18 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := paramsMap["limit"].(int); ok && val > 0 {
 		limit = val
 	} else if ok && val < 0 {
-		return nil, util.NewAgentError("limit must be greater than or equal to 1", nil)
+		return nil, fmt.Errorf("limit must be greater than or equal to 1")
 	}
 
 	tokenString := ""
 	if source.UseClientAuthorization() {
 		tokenString, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("failed to parse access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("failed to parse access token: %w", err)
 		}
 	}
 
-	resp, err := source.ListLogNames(ctx, limit, tokenString)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListLogNames(ctx, limit, tokenString)
 }
 
 func (t Tool) ParseParams(data map[string]any, claimsMap map[string]map[string]any) (parameters.ParamValues, error) {

internal/tools/cloudloggingadmin/cloudloggingadminlistresourcetypes/cloudloggingadminlistresourcetypes.go

@@ -16,13 +16,11 @@ package cloudloggingadminlistresourcetypes
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -86,25 +84,21 @@ type Tool struct {
 	mcpManifest tools.McpManifest
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	tokenString := ""
 	if source.UseClientAuthorization() {
 		tokenString, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("failed to parse access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("failed to parse access token: %w", err)
 		}
 	}
 
-	resp, err := source.ListResourceTypes(ctx, tokenString)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListResourceTypes(ctx, tokenString)
 }
 
 func (t Tool) ParseParams(data map[string]any, claimsMap map[string]map[string]any) (parameters.ParamValues, error) {

internal/tools/cloudloggingadmin/cloudloggingadminquerylogs/cloudloggingadminquerylogs.go

@@ -16,7 +16,6 @@ package cloudloggingadminquerylogs
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"time"
 
 	"github.com/goccy/go-yaml"
@@ -24,7 +23,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	cla "github.com/googleapis/genai-toolbox/internal/sources/cloudloggingadmin"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -106,10 +104,10 @@ type Tool struct {
 	mcpManifest tools.McpManifest
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	// Parse parameters
@@ -121,7 +119,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := paramsMap["limit"].(int); ok && val > 0 {
 		limit = val
 	} else if ok && val < 0 {
-		return nil, util.NewAgentError("limit must be greater than or equal to 1", nil)
+		return nil, fmt.Errorf("limit must be greater than or equal to 1")
 	}
 
 	// Check for verbosity of output
@@ -131,7 +129,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	var filter string
 	if f, ok := paramsMap["filter"].(string); ok {
 		if len(f) == 0 {
-			return nil, util.NewAgentError("filter cannot be empty if provided", nil)
+			return nil, fmt.Errorf("filter cannot be empty if provided")
 		}
 		filter = f
 	}
@@ -140,7 +138,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	var startTime string
 	if val, ok := paramsMap["startTime"].(string); ok && val != "" {
 		if _, err := time.Parse(time.RFC3339, val); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("startTime must be in RFC3339 format (e.g., 2025-12-09T00:00:00Z): %v", err), err)
+			return nil, fmt.Errorf("startTime must be in RFC3339 format (e.g., 2025-12-09T00:00:00Z): %w", err)
 		}
 		startTime = val
 	} else {
@@ -151,7 +149,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	var endTime string
 	if val, ok := paramsMap["endTime"].(string); ok && val != "" {
 		if _, err := time.Parse(time.RFC3339, val); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("endTime must be in RFC3339 format (e.g., 2025-12-09T23:59:59Z): %v", err), err)
+			return nil, fmt.Errorf("endTime must be in RFC3339 format (e.g., 2025-12-09T23:59:59Z): %w", err)
 		}
 		endTime = val
 	}
@@ -160,7 +158,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.UseClientAuthorization() {
 		tokenString, err = accessToken.ParseBearerToken()
 		if err != nil {
-			return nil, util.NewClientServerError("failed to parse access token", http.StatusUnauthorized, err)
+			return nil, fmt.Errorf("failed to parse access token: %w", err)
 		}
 	}
 
@@ -173,11 +171,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		Limit:       limit,
 	}
 
-	resp, err := source.QueryLogs(ctx, queryParams, tokenString)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.QueryLogs(ctx, queryParams, tokenString)
 }
 
 func (t Tool) ParseParams(data map[string]any, claimsMap map[string]map[string]any) (parameters.ParamValues, error) {

internal/tools/cloudmonitoring/cloudmonitoring.go

@@ -23,7 +23,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -94,26 +93,22 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	projectID, ok := paramsMap["projectId"].(string)
 	if !ok {
-		return nil, util.NewAgentError("projectId parameter not found or not a string", nil)
+		return nil, fmt.Errorf("projectId parameter not found or not a string")
 	}
 	query, ok := paramsMap["query"].(string)
 	if !ok {
-		return nil, util.NewAgentError("query parameter not found or not a string", nil)
+		return nil, fmt.Errorf("query parameter not found or not a string")
 	}
-	resp, err := source.RunQuery(projectID, query)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RunQuery(projectID, query)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlcloneinstance/cloudsqlcloneinstance.go

@@ -17,13 +17,11 @@ package cloudsqlcloneinstance
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	sqladmin "google.golang.org/api/sqladmin/v1"
 )
@@ -126,35 +124,31 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'project' parameter: %v", paramsMap["project"]), nil)
+		return nil, fmt.Errorf("error casting 'project' parameter: %v", paramsMap["project"])
 	}
 	sourceInstanceName, ok := paramsMap["sourceInstanceName"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'sourceInstanceName' parameter: %v", paramsMap["sourceInstanceName"]), nil)
+		return nil, fmt.Errorf("error casting 'sourceInstanceName' parameter: %v", paramsMap["sourceInstanceName"])
 	}
 	destinationInstanceName, ok := paramsMap["destinationInstanceName"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'destinationInstanceName' parameter: %v", paramsMap["destinationInstanceName"]), nil)
+		return nil, fmt.Errorf("error casting 'destinationInstanceName' parameter: %v", paramsMap["destinationInstanceName"])
 	}
 
 	pointInTime, _ := paramsMap["pointInTime"].(string)
 	preferredZone, _ := paramsMap["preferredZone"].(string)
 	preferredSecondaryZone, _ := paramsMap["preferredSecondaryZone"].(string)
 
-	resp, err := source.CloneInstance(ctx, project, sourceInstanceName, destinationInstanceName, pointInTime, preferredZone, preferredSecondaryZone, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CloneInstance(ctx, project, sourceInstanceName, destinationInstanceName, pointInTime, preferredZone, preferredSecondaryZone, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlcreatebackup/cloudsqlcreatebackup.go

@@ -17,13 +17,11 @@ package cloudsqlcreatebackup
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/sqladmin/v1"
 )
@@ -122,30 +120,26 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'project' parameter: %v", paramsMap["project"]), nil)
+		return nil, fmt.Errorf("error casting 'project' parameter: %v", paramsMap["project"])
 	}
 	instance, ok := paramsMap["instance"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'instance' parameter: %v", paramsMap["instance"]), nil)
+		return nil, fmt.Errorf("error casting 'instance' parameter: %v", paramsMap["instance"])
 	}
 
 	location, _ := paramsMap["location"].(string)
 	description, _ := paramsMap["backup_description"].(string)
 
-	resp, err := source.InsertBackupRun(ctx, project, instance, location, description, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.InsertBackupRun(ctx, project, instance, location, description, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlcreatedatabase/cloudsqlcreatedatabase.go

@@ -17,13 +17,11 @@ package cloudsqlcreatedatabase
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -119,31 +117,27 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	instance, ok := paramsMap["instance"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'instance' parameter", nil)
+		return nil, fmt.Errorf("missing 'instance' parameter")
 	}
 	name, ok := paramsMap["name"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'name' parameter", nil)
+		return nil, fmt.Errorf("missing 'name' parameter")
 	}
-	resp, err := source.CreateDatabase(ctx, name, project, instance, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateDatabase(ctx, name, project, instance, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlcreateusers/cloudsqlcreateusers.go

@@ -17,13 +17,11 @@ package cloudsqlcreateusers
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -121,34 +119,30 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	instance, ok := paramsMap["instance"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'instance' parameter", nil)
+		return nil, fmt.Errorf("missing 'instance' parameter")
 	}
 	name, ok := paramsMap["name"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'name' parameter", nil)
+		return nil, fmt.Errorf("missing 'name' parameter")
 	}
 
 	iamUser, _ := paramsMap["iamUser"].(bool)
 	password, _ := paramsMap["password"].(string)
-	resp, err := source.CreateUsers(ctx, project, instance, name, password, iamUser, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateUsers(ctx, project, instance, name, password, iamUser, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlgetinstances/cloudsqlgetinstances.go

@@ -17,13 +17,11 @@ package cloudsqlgetinstances
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -119,27 +117,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	projectId, ok := paramsMap["projectId"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'projectId' parameter", nil)
+		return nil, fmt.Errorf("missing 'projectId' parameter")
 	}
 	instanceId, ok := paramsMap["instanceId"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'instanceId' parameter", nil)
+		return nil, fmt.Errorf("missing 'instanceId' parameter")
 	}
-	resp, err := source.GetInstance(ctx, projectId, instanceId, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetInstance(ctx, projectId, instanceId, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqllistdatabases/cloudsqllistdatabases.go

@@ -17,13 +17,11 @@ package cloudsqllistdatabases
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -118,27 +116,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	instance, ok := paramsMap["instance"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'instance' parameter", nil)
+		return nil, fmt.Errorf("missing 'instance' parameter")
 	}
-	resp, err := source.ListDatabase(ctx, project, instance, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListDatabase(ctx, project, instance, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqllistinstances/cloudsqllistinstances.go

@@ -17,13 +17,11 @@ package cloudsqllistinstances
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -117,23 +115,19 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
-	resp, err := source.ListInstance(ctx, project, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListInstance(ctx, project, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlrestorebackup/cloudsqlrestorebackup.go

@@ -17,13 +17,11 @@ package cloudsqlrestorebackup
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/sqladmin/v1"
 )
@@ -122,33 +120,29 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 
 	targetProject, ok := paramsMap["target_project"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'target_project' parameter: %v", paramsMap["target_project"]), nil)
+		return nil, fmt.Errorf("error casting 'target_project' parameter: %v", paramsMap["target_project"])
 	}
 	targetInstance, ok := paramsMap["target_instance"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'target_instance' parameter: %v", paramsMap["target_instance"]), nil)
+		return nil, fmt.Errorf("error casting 'target_instance' parameter: %v", paramsMap["target_instance"])
 	}
 	backupID, ok := paramsMap["backup_id"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'backup_id' parameter: %v", paramsMap["backup_id"]), nil)
+		return nil, fmt.Errorf("error casting 'backup_id' parameter: %v", paramsMap["backup_id"])
 	}
 	sourceProject, _ := paramsMap["source_project"].(string)
 	sourceInstance, _ := paramsMap["source_instance"].(string)
 
-	resp, err := source.RestoreBackup(ctx, targetProject, targetInstance, sourceProject, sourceInstance, backupID, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.RestoreBackup(ctx, targetProject, targetInstance, sourceProject, sourceInstance, backupID, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsql/cloudsqlwaitforoperation/cloudsqlwaitforoperation.go

@@ -17,14 +17,12 @@ package cloudsqlwaitforoperation
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"time"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/sqladmin/v1"
 )
@@ -212,21 +210,21 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	operationID, ok := paramsMap["operation"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'operation' parameter", nil)
+		return nil, fmt.Errorf("missing 'operation' parameter")
 	}
 
 	ctx, cancel := context.WithTimeout(ctx, 30*time.Minute)
@@ -234,7 +232,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	service, err := source.GetService(ctx, string(accessToken))
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, err
 	}
 
 	delay := t.Delay
@@ -246,13 +244,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	for retries < maxRetries {
 		select {
 		case <-ctx.Done():
-			return nil, util.NewClientServerError("timed out waiting for operation", http.StatusRequestTimeout, ctx.Err())
+			return nil, fmt.Errorf("timed out waiting for operation: %w", ctx.Err())
 		default:
 		}
 
 		op, err := source.GetWaitForOperations(ctx, service, project, operationID, cloudSQLConnectionMessageTemplate, delay)
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
+			return nil, err
 		} else if op != nil {
 			return op, nil
 		}
@@ -264,7 +262,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		}
 		retries++
 	}
-	return nil, util.NewClientServerError("exceeded max retries waiting for operation", http.StatusGatewayTimeout, fmt.Errorf("exceeded max retries"))
+	return nil, fmt.Errorf("exceeded max retries waiting for operation")
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsqlmssql/cloudsqlmssqlcreateinstance/cloudsqlmssqlcreateinstance.go

@@ -17,14 +17,12 @@ package cloudsqlmssqlcreateinstance
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/sqladmin/v1"
 )
@@ -123,33 +121,33 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'project' parameter: %s", paramsMap["project"]), nil)
+		return nil, fmt.Errorf("error casting 'project' parameter: %s", paramsMap["project"])
 	}
 	name, ok := paramsMap["name"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'name' parameter: %s", paramsMap["name"]), nil)
+		return nil, fmt.Errorf("error casting 'name' parameter: %s", paramsMap["name"])
 	}
 	dbVersion, ok := paramsMap["databaseVersion"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'databaseVersion' parameter: %s", paramsMap["databaseVersion"]), nil)
+		return nil, fmt.Errorf("error casting 'databaseVersion' parameter: %s", paramsMap["databaseVersion"])
 	}
 	rootPassword, ok := paramsMap["rootPassword"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'rootPassword' parameter: %s", paramsMap["rootPassword"]), nil)
+		return nil, fmt.Errorf("error casting 'rootPassword' parameter: %s", paramsMap["rootPassword"])
 	}
 	editionPreset, ok := paramsMap["editionPreset"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'editionPreset' parameter: %s", paramsMap["editionPreset"]), nil)
+		return nil, fmt.Errorf("error casting 'editionPreset' parameter: %s", paramsMap["editionPreset"])
 	}
 	settings := sqladmin.Settings{}
 	switch strings.ToLower(editionPreset) {
@@ -166,13 +164,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		settings.DataDiskSizeGb = 100
 		settings.DataDiskType = "PD_SSD"
 	default:
-		return nil, util.NewAgentError(fmt.Sprintf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset), nil)
+		return nil, fmt.Errorf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset)
 	}
-	resp, err := source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsqlmysql/cloudsqlmysqlcreateinstance/cloudsqlmysqlcreateinstance.go

@@ -17,14 +17,12 @@ package cloudsqlmysqlcreateinstance
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	sqladmin "google.golang.org/api/sqladmin/v1"
 )
@@ -123,33 +121,33 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	name, ok := paramsMap["name"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'name' parameter", nil)
+		return nil, fmt.Errorf("missing 'name' parameter")
 	}
 	dbVersion, ok := paramsMap["databaseVersion"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'databaseVersion' parameter", nil)
+		return nil, fmt.Errorf("missing 'databaseVersion' parameter")
 	}
 	rootPassword, ok := paramsMap["rootPassword"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'rootPassword' parameter", nil)
+		return nil, fmt.Errorf("missing 'rootPassword' parameter")
 	}
 	editionPreset, ok := paramsMap["editionPreset"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'editionPreset' parameter", nil)
+		return nil, fmt.Errorf("missing 'editionPreset' parameter")
 	}
 
 	settings := sqladmin.Settings{}
@@ -167,14 +165,10 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		settings.DataDiskSizeGb = 100
 		settings.DataDiskType = "PD_SSD"
 	default:
-		return nil, util.NewAgentError(fmt.Sprintf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset), nil)
+		return nil, fmt.Errorf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset)
 	}
 
-	resp, err := source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsqlpg/cloudsqlpgcreateinstances/cloudsqlpgcreateinstances.go

@@ -17,14 +17,12 @@ package cloudsqlpgcreateinstances
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	sqladmin "google.golang.org/api/sqladmin/v1"
 )
@@ -123,33 +121,33 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'project' parameter", nil)
+		return nil, fmt.Errorf("missing 'project' parameter")
 	}
 	name, ok := paramsMap["name"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'name' parameter", nil)
+		return nil, fmt.Errorf("missing 'name' parameter")
 	}
 	dbVersion, ok := paramsMap["databaseVersion"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'databaseVersion' parameter", nil)
+		return nil, fmt.Errorf("missing 'databaseVersion' parameter")
 	}
 	rootPassword, ok := paramsMap["rootPassword"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'rootPassword' parameter", nil)
+		return nil, fmt.Errorf("missing 'rootPassword' parameter")
 	}
 	editionPreset, ok := paramsMap["editionPreset"].(string)
 	if !ok {
-		return nil, util.NewAgentError("missing 'editionPreset' parameter", nil)
+		return nil, fmt.Errorf("missing 'editionPreset' parameter")
 	}
 
 	settings := sqladmin.Settings{}
@@ -167,13 +165,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		settings.DataDiskSizeGb = 100
 		settings.DataDiskType = "PD_SSD"
 	default:
-		return nil, util.NewAgentError(fmt.Sprintf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset), nil)
+		return nil, fmt.Errorf("invalid 'editionPreset': %q. Must be either 'Production' or 'Development'", editionPreset)
 	}
-	resp, err := source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.CreateInstance(ctx, project, name, dbVersion, rootPassword, settings, string(accessToken))
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/cloudsqlpg/cloudsqlpgupgradeprecheck/cloudsqlpgupgradeprecheck.go

@@ -17,14 +17,12 @@ package cloudsqlpgupgradeprecheck
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"time"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	sqladmin "google.golang.org/api/sqladmin/v1"
 )
@@ -134,31 +132,31 @@ func (t Tool) ToConfig() tools.ToolConfig {
 }
 
 // Invoke executes the tool's logic.
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 
 	project, ok := paramsMap["project"].(string)
 	if !ok || project == "" {
-		return nil, util.NewAgentError("missing or empty 'project' parameter", nil)
+		return nil, fmt.Errorf("missing or empty 'project' parameter")
 	}
 	instanceName, ok := paramsMap["instance"].(string)
 	if !ok || instanceName == "" {
-		return nil, util.NewAgentError("missing or empty 'instance' parameter", nil)
+		return nil, fmt.Errorf("missing or empty 'instance' parameter")
 	}
 	targetVersion, ok := paramsMap["targetDatabaseVersion"].(string)
 	if !ok || targetVersion == "" {
 		// This should not happen due to the default value
-		return nil, util.NewAgentError("missing or empty 'targetDatabaseVersion' parameter", nil)
+		return nil, fmt.Errorf("missing or empty 'targetDatabaseVersion' parameter")
 	}
 
 	service, err := source.GetService(ctx, string(accessToken))
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to get HTTP client from source: %w", err)
 	}
 
 	reqBody := &sqladmin.InstancesPreCheckMajorVersionUpgradeRequest{
@@ -170,7 +168,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	call := service.Instances.PreCheckMajorVersionUpgrade(project, instanceName, reqBody).Context(ctx)
 	op, err := call.Do()
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, fmt.Errorf("failed to start pre-check operation: %w", err)
 	}
 
 	const pollTimeout = 20 * time.Second
@@ -179,7 +177,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	for time.Now().Before(cutoffTime) {
 		currentOp, err := service.Operations.Get(project, op.Name).Context(ctx).Do()
 		if err != nil {
-			return nil, util.ProcessGcpError(err)
+			return nil, fmt.Errorf("failed to get operation status: %w", err)
 		}
 
 		if currentOp.Status == "DONE" {
@@ -188,7 +186,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 				if currentOp.Error.Errors[0].Code != "" {
 					errMsg = fmt.Sprintf("%s (Code: %s)", errMsg, currentOp.Error.Errors[0].Code)
 				}
-				return nil, util.NewClientServerError(errMsg, http.StatusInternalServerError, fmt.Errorf("pre-check operation failed with error: %s", errMsg))
+				return nil, fmt.Errorf("%s", errMsg)
 			}
 
 			var preCheckItems []*sqladmin.PreCheckResponse
@@ -201,7 +199,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 		select {
 		case <-ctx.Done():
-			return nil, util.NewClientServerError("timed out waiting for operation", http.StatusRequestTimeout, ctx.Err())
+			return nil, ctx.Err()
 		case <-time.After(5 * time.Second):
 		}
 	}

internal/tools/couchbase/couchbase.go

@@ -17,14 +17,12 @@ package couchbase
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"github.com/couchbase/gocb/v2"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -60,6 +58,7 @@ type Config struct {
 	TemplateParameters parameters.Parameters `yaml:"templateParameters"`
 }
 
+// validate interface
 var _ tools.ToolConfig = Config{}
 
 func (cfg Config) ToolConfigType() string {
@@ -73,6 +72,7 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 	}
 
 	mcpManifest := tools.GetMcpManifest(cfg.Name, cfg.Description, cfg.AuthRequired, allParameters, nil)
+	// finish tool setup
 	t := Tool{
 		Config:      cfg,
 		AllParams:   allParameters,
@@ -82,6 +82,7 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 	return t, nil
 }
 
+// validate interface
 var _ tools.Tool = Tool{}
 
 type Tool struct {
@@ -95,28 +96,23 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	namedParamsMap := params.AsMap()
 	newStatement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, namedParamsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params %w", err)
 	}
 
 	newParams, err := parameters.GetParams(t.Parameters, namedParamsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract standard params", err)
+		return nil, fmt.Errorf("unable to extract standard params %w", err)
 	}
-
-	resp, err := source.RunSQL(newStatement, newParams)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(newStatement, newParams)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/dataform/dataformcompilelocal/dataformcompilelocal.go

@@ -24,7 +24,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -87,19 +86,18 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	paramsMap := params.AsMap()
 
 	projectDir, ok := paramsMap["project_dir"].(string)
 	if !ok || projectDir == "" {
-		return nil, util.NewAgentError("error casting 'project_dir' to string or invalid value", nil)
+		return nil, fmt.Errorf("error casting 'project_dir' to string or invalid value")
 	}
 
 	cmd := exec.CommandContext(ctx, "dataform", "compile", projectDir, "--json")
 	output, err := cmd.CombinedOutput()
 	if err != nil {
-		// Compilation failures are considered AgentErrors (invalid user code/project)
-		return nil, util.NewAgentError(fmt.Sprintf("error executing dataform compile: %v\nOutput: %s", err, string(output)), err)
+		return nil, fmt.Errorf("error executing dataform compile: %w\nOutput: %s", err, string(output))
 	}
 
 	return strings.TrimSpace(string(output)), nil

internal/tools/dataplex/dataplexlookupentry/dataplexlookupentry.go

@@ -17,14 +17,12 @@ package dataplexlookupentry
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	dataplexpb "cloud.google.com/go/dataplex/apiv1/dataplexpb"
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -112,10 +110,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
@@ -124,14 +122,10 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	view, _ := paramsMap["view"].(int)
 	aspectTypeSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["aspectTypes"].([]any), "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("can't convert aspectTypes to array of strings: %s", err), err)
+		return nil, fmt.Errorf("can't convert aspectTypes to array of strings: %s", err)
 	}
 	aspectTypes := aspectTypeSlice.([]string)
-	resp, err := source.LookupEntry(ctx, name, view, aspectTypes, entry)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.LookupEntry(ctx, name, view, aspectTypes, entry)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/dataplex/dataplexsearchaspecttypes/dataplexsearchaspecttypes.go

@@ -17,14 +17,12 @@ package dataplexsearchaspecttypes
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"cloud.google.com/go/dataplex/apiv1/dataplexpb"
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -95,29 +93,16 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
-	query, ok := paramsMap["query"].(string)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'query' parameter: %v", paramsMap["query"]), nil)
-	}
-	pageSize, ok := paramsMap["pageSize"].(int)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'pageSize' parameter: %v", paramsMap["pageSize"]), nil)
-	}
-	orderBy, ok := paramsMap["orderBy"].(string)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'orderBy' parameter: %v", paramsMap["orderBy"]), nil)
-	}
-	resp, err := source.SearchAspectTypes(ctx, query, pageSize, orderBy)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	query, _ := paramsMap["query"].(string)
+	pageSize, _ := paramsMap["pageSize"].(int)
+	orderBy, _ := paramsMap["orderBy"].(string)
+	return source.SearchAspectTypes(ctx, query, pageSize, orderBy)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/dataplex/dataplexsearchentries/dataplexsearchentries.go

@@ -17,14 +17,12 @@ package dataplexsearchentries
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	"cloud.google.com/go/dataplex/apiv1/dataplexpb"
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -95,29 +93,16 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
-	query, ok := paramsMap["query"].(string)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'query' parameter: %v", paramsMap["query"]), nil)
-	}
-	pageSize, ok := paramsMap["pageSize"].(int)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'pageSize' parameter: %v", paramsMap["pageSize"]), nil)
-	}
-	orderBy, ok := paramsMap["orderBy"].(string)
-	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("error casting 'orderBy' parameter: %v", paramsMap["orderBy"]), nil)
-	}
-	resp, err := source.SearchEntries(ctx, query, pageSize, orderBy)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	query, _ := paramsMap["query"].(string)
+	pageSize, _ := paramsMap["pageSize"].(int)
+	orderBy, _ := paramsMap["orderBy"].(string)
+	return source.SearchEntries(ctx, query, pageSize, orderBy)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/dgraph/dgraph.go

@@ -17,14 +17,12 @@ package dgraph
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/sources/dgraph"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -93,16 +91,12 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
-	resp, err := source.RunSQL(t.Statement, params, t.IsQuery, t.Timeout)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(t.Statement, params, t.IsQuery, t.Timeout)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/elasticsearch/elasticsearchesql/elasticsearchesql.go

@@ -17,11 +17,9 @@ package elasticsearchesql
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"time"
 
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 
 	"github.com/goccy/go-yaml"
@@ -91,10 +89,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	var cancel context.CancelFunc
@@ -121,15 +119,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	for _, param := range t.Parameters {
 		if param.GetType() == "array" {
-			return nil, util.NewAgentError("array parameters are not supported yet", nil)
+			return nil, fmt.Errorf("array parameters are not supported yet")
 		}
 		sqlParams = append(sqlParams, map[string]any{param.GetName(): paramMap[param.GetName()]})
 	}
-	resp, err := source.RunSQL(ctx, t.Format, query, sqlParams)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, t.Format, query, sqlParams)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firebird/firebirdexecutesql/firebirdexecutesql.go

@@ -18,7 +18,6 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
@@ -91,30 +90,25 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
-	sqlStr, ok := paramsMap["sql"].(string)
+	sql, ok := paramsMap["sql"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("unable to cast parameter 'sql' to string: %v", paramsMap["sql"]), nil)
+		return nil, fmt.Errorf("unable to get cast %s", paramsMap["sql"])
 	}
 
 	// Log the query executed for debugging.
 	logger, err := util.LoggerFromContext(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("error getting logger", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting logger: %s", err)
 	}
-	logger.DebugContext(ctx, fmt.Sprintf("executing `%s` tool query: %s", resourceType, sqlStr))
-
-	resp, err := source.RunSQL(ctx, sqlStr, nil)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	logger.DebugContext(ctx, fmt.Sprintf("executing `%s` tool query: %s", resourceType, sql))
+	return source.RunSQL(ctx, sql, nil)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firebird/firebirdsql/firebirdsql.go

@@ -18,14 +18,12 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
-	"net/http"
 	"strings"
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -100,21 +98,21 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
 	statement, err := parameters.ResolveTemplateParams(t.TemplateParameters, t.Statement, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract template params", err)
+		return nil, fmt.Errorf("unable to extract template params: %w", err)
 	}
 
 	newParams, err := parameters.GetParams(t.Parameters, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("unable to extract standard params", err)
+		return nil, fmt.Errorf("unable to extract standard params: %w", err)
 	}
 
 	namedArgs := make([]any, 0, len(newParams))
@@ -129,12 +127,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			namedArgs = append(namedArgs, value)
 		}
 	}
-
-	resp, err := source.RunSQL(ctx, statement, namedArgs)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunSQL(ctx, statement, namedArgs)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestoreadddocuments/firestoreadddocuments.go

@@ -17,15 +17,13 @@ package firestoreadddocuments
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	firestoreapi "cloud.google.com/go/firestore"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -130,32 +128,32 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	// Get collection path
 	collectionPath, ok := mapParams[collectionPathKey].(string)
 	if !ok || collectionPath == "" {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter", collectionPathKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter", collectionPathKey)
 	}
 	// Validate collection path
-	if err := fsUtil.ValidateCollectionPath(collectionPath); err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid collection path: %v", err), err)
+	if err := util.ValidateCollectionPath(collectionPath); err != nil {
+		return nil, fmt.Errorf("invalid collection path: %w", err)
 	}
 	// Get document data
 	documentDataRaw, ok := mapParams[documentDataKey]
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter", documentDataKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter", documentDataKey)
 	}
 	// Convert the document data from JSON format to Firestore format
 	// The client is passed to handle referenceValue types
-	documentData, err := fsUtil.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
+	documentData, err := util.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to convert document data: %v", err), err)
+		return nil, fmt.Errorf("failed to convert document data: %w", err)
 	}
 
 	// Get return document data flag
@@ -163,11 +161,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := mapParams[returnDocumentDataKey].(bool); ok {
 		returnData = val
 	}
-	resp, err := source.AddDocuments(ctx, collectionPath, documentData, returnData)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.AddDocuments(ctx, collectionPath, documentData, returnData)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestoredeletedocuments/firestoredeletedocuments.go

@@ -17,15 +17,13 @@ package firestoredeletedocuments
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	firestoreapi "cloud.google.com/go/firestore"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -96,43 +94,39 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	documentPathsRaw, ok := mapParams[documentPathsKey].([]any)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected an array", documentPathsKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected an array", documentPathsKey)
 	}
 	if len(documentPathsRaw) == 0 {
-		return nil, util.NewAgentError(fmt.Sprintf("'%s' parameter cannot be empty", documentPathsKey), nil)
+		return nil, fmt.Errorf("'%s' parameter cannot be empty", documentPathsKey)
 	}
 
 	// Use ConvertAnySliceToTyped to convert the slice
 	typedSlice, err := parameters.ConvertAnySliceToTyped(documentPathsRaw, "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to convert document paths: %v", err), err)
+		return nil, fmt.Errorf("failed to convert document paths: %w", err)
 	}
 
 	documentPaths, ok := typedSlice.([]string)
 	if !ok {
-		return nil, util.NewAgentError("unexpected type conversion error for document paths", nil)
+		return nil, fmt.Errorf("unexpected type conversion error for document paths")
 	}
 
 	// Validate each document path
 	for i, path := range documentPaths {
-		if err := fsUtil.ValidateDocumentPath(path); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid document path at index %d: %v", i, err), err)
+		if err := util.ValidateDocumentPath(path); err != nil {
+			return nil, fmt.Errorf("invalid document path at index %d: %w", i, err)
 		}
 	}
-	resp, err := source.DeleteDocuments(ctx, documentPaths)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.DeleteDocuments(ctx, documentPaths)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestoregetdocuments/firestoregetdocuments.go

@@ -17,15 +17,13 @@ package firestoregetdocuments
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	firestoreapi "cloud.google.com/go/firestore"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -96,44 +94,40 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
 	documentPathsRaw, ok := mapParams[documentPathsKey].([]any)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected an array", documentPathsKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter; expected an array", documentPathsKey)
 	}
 
 	if len(documentPathsRaw) == 0 {
-		return nil, util.NewAgentError(fmt.Sprintf("'%s' parameter cannot be empty", documentPathsKey), nil)
+		return nil, fmt.Errorf("'%s' parameter cannot be empty", documentPathsKey)
 	}
 
 	// Use ConvertAnySliceToTyped to convert the slice
 	typedSlice, err := parameters.ConvertAnySliceToTyped(documentPathsRaw, "string")
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to convert document paths: %v", err), err)
+		return nil, fmt.Errorf("failed to convert document paths: %w", err)
 	}
 
 	documentPaths, ok := typedSlice.([]string)
 	if !ok {
-		return nil, util.NewAgentError("unexpected type conversion error for document paths", nil)
+		return nil, fmt.Errorf("unexpected type conversion error for document paths")
 	}
 
 	// Validate each document path
 	for i, path := range documentPaths {
-		if err := fsUtil.ValidateDocumentPath(path); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid document path at index %d: %v", i, err), err)
+		if err := util.ValidateDocumentPath(path); err != nil {
+			return nil, fmt.Errorf("invalid document path at index %d: %w", i, err)
 		}
 	}
-	resp, err := source.GetDocuments(ctx, documentPaths)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetDocuments(ctx, documentPaths)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestoregetrules/firestoregetrules.go

@@ -17,13 +17,11 @@ package firestoregetrules
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/firebaserules/v1"
 )
@@ -94,16 +92,12 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
-	resp, err := source.GetRules(ctx)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.GetRules(ctx)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestorelistcollections/firestorelistcollections.go

@@ -17,15 +17,13 @@ package firestorelistcollections
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	firestoreapi "cloud.google.com/go/firestore"
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -97,10 +95,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
@@ -109,15 +107,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	parentPath, _ := mapParams[parentPathKey].(string)
 	if parentPath != "" {
 		// Validate parent document path
-		if err := fsUtil.ValidateDocumentPath(parentPath); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("invalid parent document path: %v", err), err)
+		if err := util.ValidateDocumentPath(parentPath); err != nil {
+			return nil, fmt.Errorf("invalid parent document path: %w", err)
 		}
 	}
-	resp, err := source.ListCollections(ctx, parentPath)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ListCollections(ctx, parentPath)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/firestore/firestorequery/firestorequery.go

@@ -18,7 +18,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net/http"
 	"strconv"
 	"strings"
 
@@ -27,8 +26,7 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -160,16 +158,16 @@ var validOperators = map[string]bool{
 }
 
 // Invoke executes the Firestore query based on the provided parameters
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 	paramsMap := params.AsMap()
 	// Process collection path with template substitution
 	collectionPath, err := parameters.PopulateTemplate("collectionPath", t.CollectionPath, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to process collection path: %v", err), err)
+		return nil, fmt.Errorf("failed to process collection path: %w", err)
 	}
 
 	var filter firestoreapi.EntityFilter
@@ -178,13 +176,13 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		// Apply template substitution to filters
 		filtersJSON, err := parameters.PopulateTemplateWithJSON("filters", t.Filters, paramsMap)
 		if err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("failed to process filters template: %v", err), err)
+			return nil, fmt.Errorf("failed to process filters template: %w", err)
 		}
 
 		// Parse the simplified filter format
 		var simplifiedFilter SimplifiedFilter
 		if err := json.Unmarshal([]byte(filtersJSON), &simplifiedFilter); err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("failed to parse filters: %v", err), err)
+			return nil, fmt.Errorf("failed to parse filters: %w", err)
 		}
 
 		// Convert simplified filter to Firestore filter
@@ -193,17 +191,17 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Process and apply ordering
 	orderBy, err := t.getOrderBy(paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to process order by: %v", err), err)
+		return nil, err
 	}
 	// Process select fields
 	selectFields, err := t.processSelectFields(paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to process select fields: %v", err), err)
+		return nil, err
 	}
 	// Process and apply limit
 	limit, err := t.getLimit(paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to process limit: %v", err), err)
+		return nil, err
 	}
 
 	// prevent panic when accessing orderBy incase it is nil
@@ -217,14 +215,10 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Build the query
 	query, err := source.BuildQuery(collectionPath, filter, selectFields, orderByField, orderByDirection, limit, t.AnalyzeQuery)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, err
 	}
 	// Execute the query and return results
-	resp, err := source.ExecuteQuery(ctx, query, t.AnalyzeQuery)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ExecuteQuery(ctx, query, t.AnalyzeQuery)
 }
 
 // convertToFirestoreFilter converts simplified filter format to Firestore EntityFilter
@@ -261,7 +255,7 @@ func (t Tool) convertToFirestoreFilter(source compatibleSource, filter Simplifie
 	if filter.Field != "" && filter.Op != "" && filter.Value != nil {
 		if validOperators[filter.Op] {
 			// Convert the value using the Firestore native JSON converter
-			convertedValue, err := fsUtil.JSONToFirestoreValue(filter.Value, source.FirestoreClient())
+			convertedValue, err := util.JSONToFirestoreValue(filter.Value, source.FirestoreClient())
 			if err != nil {
 				// If conversion fails, use the original value
 				convertedValue = filter.Value
@@ -373,7 +367,7 @@ func (t Tool) getLimit(params map[string]any) (int, error) {
 		if processedValue != "" {
 			parsedLimit, err := strconv.Atoi(processedValue)
 			if err != nil {
-				return 0, err
+				return 0, fmt.Errorf("failed to parse limit value '%s': %w", processedValue, err)
 			}
 			limit = parsedLimit
 		}

internal/tools/firestore/firestorequerycollection/firestorequerycollection.go

@@ -18,7 +18,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net/http"
 	"strings"
 
 	firestoreapi "cloud.google.com/go/firestore"
@@ -26,8 +25,7 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -232,16 +230,16 @@ func (o *OrderByConfig) GetDirection() firestoreapi.Direction {
 }
 
 // Invoke executes the Firestore query based on the provided parameters
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	// Parse parameters
 	queryParams, err := t.parseQueryParameters(params)
 	if err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("failed to parse query parameters: %v", err), err)
+		return nil, err
 	}
 
 	var filter firestoreapi.EntityFilter
@@ -272,13 +270,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Build the query
 	query, err := source.BuildQuery(queryParams.CollectionPath, filter, nil, orderByField, orderByDirection, queryParams.Limit, queryParams.AnalyzeQuery)
 	if err != nil {
-		return nil, util.ProcessGcpError(err)
+		return nil, err
 	}
-	resp, err := source.ExecuteQuery(ctx, query, queryParams.AnalyzeQuery)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ExecuteQuery(ctx, query, queryParams.AnalyzeQuery)
 }
 
 // queryParameters holds all parsed query parameters
@@ -301,7 +295,7 @@ func (t Tool) parseQueryParameters(params parameters.ParamValues) (*queryParamet
 	}
 
 	// Validate collection path
-	if err := fsUtil.ValidateCollectionPath(collectionPath); err != nil {
+	if err := util.ValidateCollectionPath(collectionPath); err != nil {
 		return nil, fmt.Errorf("invalid collection path: %w", err)
 	}
 

internal/tools/firestore/firestoreupdatedocument/firestoreupdatedocument.go

@@ -17,7 +17,6 @@ package firestoreupdatedocument
 import (
 	"context"
 	"fmt"
-	"net/http"
 	"strings"
 
 	firestoreapi "cloud.google.com/go/firestore"
@@ -25,8 +24,7 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	fsUtil "github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
-	"github.com/googleapis/genai-toolbox/internal/util"
+	"github.com/googleapis/genai-toolbox/internal/tools/firestore/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -140,10 +138,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
@@ -151,18 +149,18 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Get document path
 	documentPath, ok := mapParams[documentPathKey].(string)
 	if !ok || documentPath == "" {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter", documentPathKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter", documentPathKey)
 	}
 
 	// Validate document path
-	if err := fsUtil.ValidateDocumentPath(documentPath); err != nil {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid document path: %v", err), err)
+	if err := util.ValidateDocumentPath(documentPath); err != nil {
+		return nil, fmt.Errorf("invalid document path: %w", err)
 	}
 
 	// Get document data
 	documentDataRaw, ok := mapParams[documentDataKey]
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter", documentDataKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter", documentDataKey)
 	}
 
 	// Get update mask if provided
@@ -172,11 +170,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 			// Use ConvertAnySliceToTyped to convert the slice
 			typedSlice, err := parameters.ConvertAnySliceToTyped(updateMaskArray, "string")
 			if err != nil {
-				return nil, util.NewAgentError(fmt.Sprintf("failed to convert update mask: %v", err), err)
+				return nil, fmt.Errorf("failed to convert update mask: %w", err)
 			}
 			updatePaths, ok = typedSlice.([]string)
 			if !ok {
-				return nil, util.NewAgentError("unexpected type conversion error for update mask", nil)
+				return nil, fmt.Errorf("unexpected type conversion error for update mask")
 			}
 		}
 	}
@@ -186,15 +184,15 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if len(updatePaths) > 0 {
 
 		// Convert document data without delete markers
-		dataMap, err := fsUtil.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
+		dataMap, err := util.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
 		if err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("failed to convert document data: %v", err), err)
+			return nil, fmt.Errorf("failed to convert document data: %w", err)
 		}
 
 		// Ensure it's a map
 		dataMapTyped, ok := dataMap.(map[string]interface{})
 		if !ok {
-			return nil, util.NewAgentError("document data must be a map", nil)
+			return nil, fmt.Errorf("document data must be a map")
 		}
 
 		for _, path := range updatePaths {
@@ -212,9 +210,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		}
 	} else {
 		// Update all fields in the document data (merge)
-		documentData, err = fsUtil.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
+		documentData, err = util.JSONToFirestoreValue(documentDataRaw, source.FirestoreClient())
 		if err != nil {
-			return nil, util.NewAgentError(fmt.Sprintf("failed to convert document data: %v", err), err)
+			return nil, fmt.Errorf("failed to convert document data: %w", err)
 		}
 	}
 
@@ -223,11 +221,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if val, ok := mapParams[returnDocumentDataKey].(bool); ok {
 		returnData = val
 	}
-	resp, err := source.UpdateDocument(ctx, documentPath, updates, documentData, returnData)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.UpdateDocument(ctx, documentPath, updates, documentData, returnData)
 }
 
 // getFieldValue retrieves a value from a nested map using a dot-separated path

internal/tools/firestore/firestorevalidaterules/firestorevalidaterules.go

@@ -17,13 +17,11 @@ package firestorevalidaterules
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 	"google.golang.org/api/firebaserules/v1"
 )
@@ -108,10 +106,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	mapParams := params.AsMap()
@@ -119,13 +117,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Get source parameter
 	sourceParam, ok := mapParams[sourceKey].(string)
 	if !ok || sourceParam == "" {
-		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter", sourceKey), nil)
+		return nil, fmt.Errorf("invalid or missing '%s' parameter", sourceKey)
 	}
-	resp, err := source.ValidateRules(ctx, sourceParam)
-	if err != nil {
-		return nil, util.ProcessGcpError(err)
-	}
-	return resp, nil
+	return source.ValidateRules(ctx, sourceParam)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/http/http.go

@@ -17,18 +17,18 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"maps"
 	"net/http"
 	"net/url"
 	"slices"
 	"strings"
+
+	"maps"
 	"text/template"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 )
 
@@ -226,10 +226,10 @@ func getHeaders(headerParams parameters.Parameters, defaultHeaders map[string]st
 	return allHeaders, nil
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	paramsMap := params.AsMap()
@@ -237,35 +237,27 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Calculate request body
 	requestBody, err := getRequestBody(t.BodyParams, t.RequestBody, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("error populating request body", err)
+		return nil, fmt.Errorf("error populating request body: %s", err)
 	}
 
 	// Calculate URL
 	urlString, err := getURL(source.HttpBaseURL(), t.Path, t.PathParams, t.QueryParams, source.HttpQueryParams(), paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("error populating path parameters", err)
+		return nil, fmt.Errorf("error populating path parameters: %s", err)
 	}
 
-	req, err := http.NewRequestWithContext(ctx, string(t.Method), urlString, strings.NewReader(requestBody))
-	if err != nil {
-		return nil, util.NewClientServerError("error creating http request", http.StatusInternalServerError, err)
-	}
+	req, _ := http.NewRequest(string(t.Method), urlString, strings.NewReader(requestBody))
 
 	// Calculate request headers
 	allHeaders, err := getHeaders(t.HeaderParams, t.Headers, paramsMap)
 	if err != nil {
-		return nil, util.NewAgentError("error populating request headers", err)
+		return nil, fmt.Errorf("error populating request headers: %s", err)
 	}
 	// Set request headers
 	for k, v := range allHeaders {
 		req.Header.Set(k, v)
 	}
-
-	resp, err := source.RunRequest(req)
-	if err != nil {
-		return nil, util.ProcessGeneralError(err)
-	}
-	return resp, nil
+	return source.RunRequest(req)
 }
 
 func (t Tool) EmbedParams(ctx context.Context, paramValues parameters.ParamValues, embeddingModelsMap map[string]embeddingmodels.EmbeddingModel) (parameters.ParamValues, error) {

internal/tools/looker/lookeradddashboardelement/lookeradddashboardelement.go

@@ -16,7 +16,6 @@ package lookeradddashboardelement
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
@@ -135,74 +134,58 @@ var (
 	visType  string = "vis"
 )
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	logger, err := util.LoggerFromContext(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("unable to get logger from ctx", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("unable to get logger from ctx: %s", err)
 	}
 
 	logger.DebugContext(ctx, "params = ", params)
 
 	wq, err := lookercommon.ProcessQueryArgs(ctx, params)
 	if err != nil {
-		return nil, util.NewAgentError("error building query request", err)
+		return nil, fmt.Errorf("error building query request: %w", err)
 	}
 
 	paramsMap := params.AsMap()
+	dashboard_id := paramsMap["dashboard_id"].(string)
+	title := paramsMap["title"].(string)
 
-	dashboard_id, ok := paramsMap["dashboard_id"].(string)
-	if !ok {
-		return nil, util.NewAgentError("dashboard_id parameter missing or invalid", nil)
-	}
-
-	title, ok := paramsMap["title"].(string)
-	if !ok {
-		title = ""
-	}
-
-	visConfig, ok := paramsMap["vis_config"].(map[string]any)
-	if !ok {
-		visConfig = make(map[string]any)
-	}
+	visConfig := paramsMap["vis_config"].(map[string]any)
 	wq.VisConfig = &visConfig
 
 	sdk, err := source.GetLookerSDK(string(accessToken))
 	if err != nil {
-		return nil, util.NewClientServerError("error getting sdk", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting sdk: %w", err)
 	}
 
 	qresp, err := sdk.CreateQuery(*wq, "id", source.LookerApiSettings())
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, fmt.Errorf("error making create query request: %w", err)
 	}
 
 	dashFilters := []any{}
 	if v, ok := paramsMap["dashboard_filters"]; ok {
 		if v != nil {
-			if df, ok := v.([]any); ok {
-				dashFilters = df
-			}
+			dashFilters = paramsMap["dashboard_filters"].([]any)
 		}
 	}
 
 	var filterables []v4.ResultMakerFilterables
 	for _, m := range dashFilters {
-		f, ok := m.(map[string]any)
-		if !ok {
-			return nil, util.NewAgentError("invalid dashboard filter structure", nil)
-		}
+		f := m.(map[string]any)
 		name, ok := f["dashboard_filter_name"].(string)
 		if !ok {
-			return nil, util.NewAgentError("error processing dashboard filter: missing dashboard_filter_name", nil)
+			return nil, fmt.Errorf("error processing dashboard filter: %w", err)
 		}
 		field, ok := f["field"].(string)
 		if !ok {
-			return nil, util.NewAgentError("error processing dashboard filter: missing field", nil)
+			return nil, fmt.Errorf("error processing dashboard filter: %w", err)
 		}
 		listener := v4.ResultMakerFilterablesListen{
 			DashboardFilterName: &name,
@@ -250,7 +233,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	resp, err := sdk.CreateDashboardElement(req, source.LookerApiSettings())
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, fmt.Errorf("error making create dashboard element request: %w", err)
 	}
 	logger.DebugContext(ctx, "resp = %v", resp)
 

internal/tools/looker/lookeradddashboardfilter/lookeradddashboardfilter.go

@@ -16,7 +16,6 @@ package lookeradddashboardfilter
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
@@ -129,54 +128,33 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	logger, err := util.LoggerFromContext(ctx)
 	if err != nil {
-		return nil, util.NewClientServerError("unable to get logger from ctx", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("unable to get logger from ctx: %s", err)
 	}
 	logger.DebugContext(ctx, "params = ", params)
 
 	paramsMap := params.AsMap()
-	dashboard_id, ok := paramsMap["dashboard_id"].(string)
-	if !ok {
-		return nil, util.NewAgentError("dashboard_id parameter missing or invalid", nil)
-	}
-	name, ok := paramsMap["name"].(string)
-	if !ok {
-		return nil, util.NewAgentError("name parameter missing or invalid", nil)
-	}
-	title, ok := paramsMap["title"].(string)
-	if !ok {
-		return nil, util.NewAgentError("title parameter missing or invalid", nil)
-	}
-	filterType, ok := paramsMap["filter_type"].(string)
-	if !ok {
-		return nil, util.NewAgentError("filter_type parameter missing or invalid", nil)
-	}
-
+	dashboard_id := paramsMap["dashboard_id"].(string)
+	name := paramsMap["name"].(string)
+	title := paramsMap["title"].(string)
+	filterType := paramsMap["filter_type"].(string)
 	switch filterType {
 	case "date_filter":
 	case "number_filter":
 	case "string_filter":
 	case "field_filter":
 	default:
-		return nil, util.NewAgentError(fmt.Sprintf("invalid filter type: %s. Must be one of date_filter, number_filter, string_filter, field_filter", filterType), nil)
-	}
-
-	allowMultipleValues, ok := paramsMap["allow_multiple_values"].(bool)
-	if !ok {
-		// defaults should handle this, but safe fallback
-		allowMultipleValues = true
-	}
-	required, ok := paramsMap["required"].(bool)
-	if !ok {
-		required = false
+		return nil, fmt.Errorf("invalid filter type: %s. Must be one of date_filter, number_filter, string_filter, field_filter", filterType)
 	}
+	allowMultipleValues := paramsMap["allow_multiple_values"].(bool)
+	required := paramsMap["required"].(bool)
 
 	req := v4.WriteCreateDashboardFilter{
 		DashboardId:         dashboard_id,
@@ -187,8 +165,9 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 		Required:            &required,
 	}
 
-	if v, ok := paramsMap["default_value"]; ok && v != nil {
-		if defaultValue, ok := v.(string); ok {
+	if v, ok := paramsMap["default_value"]; ok {
+		if v != nil {
+			defaultValue := paramsMap["default_value"].(string)
 			req.DefaultValue = &defaultValue
 		}
 	}
@@ -196,15 +175,15 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if filterType == "field_filter" {
 		model, ok := paramsMap["model"].(string)
 		if !ok || model == "" {
-			return nil, util.NewAgentError("model must be specified for field_filter type", nil)
+			return nil, fmt.Errorf("model must be specified for field_filter type")
 		}
 		explore, ok := paramsMap["explore"].(string)
 		if !ok || explore == "" {
-			return nil, util.NewAgentError("explore must be specified for field_filter type", nil)
+			return nil, fmt.Errorf("explore must be specified for field_filter type")
 		}
 		dimension, ok := paramsMap["dimension"].(string)
 		if !ok || dimension == "" {
-			return nil, util.NewAgentError("dimension must be specified for field_filter type", nil)
+			return nil, fmt.Errorf("dimension must be specified for field_filter type")
 		}
 
 		req.Model = &model
@@ -214,12 +193,12 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	sdk, err := source.GetLookerSDK(string(accessToken))
 	if err != nil {
-		return nil, util.NewClientServerError("error getting sdk", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting sdk: %w", err)
 	}
 
 	resp, err := sdk.CreateDashboardFilter(req, "name", source.LookerApiSettings())
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, fmt.Errorf("error making create dashboard filter request: %s", err)
 	}
 	logger.DebugContext(ctx, "resp = %v", resp)
 

internal/tools/looker/lookerconversationalanalytics/lookerconversationalanalytics.go

@@ -215,10 +215,10 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	var tokenStr string
@@ -226,11 +226,11 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Get credentials for the API call
 	// Use cloud-platform token source for Gemini Data Analytics API
 	if t.TokenSource == nil {
-		return nil, util.NewClientServerError("cloud-platform token source is missing", http.StatusInternalServerError, nil)
+		return nil, fmt.Errorf("cloud-platform token source is missing")
 	}
 	token, err := t.TokenSource.Token()
 	if err != nil {
-		return nil, util.NewClientServerError("failed to get token from cloud-platform token source", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to get token from cloud-platform token source: %w", err)
 	}
 	tokenStr = token.AccessToken
 
@@ -286,7 +286,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	// Call the streaming API
 	response, err := getStream(ctx, caURL, payload, headers)
 	if err != nil {
-		return nil, util.NewClientServerError("failed to get response from conversational analytics API", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("failed to get response from conversational analytics API: %w", err)
 	}
 
 	return response, nil

internal/tools/looker/lookercreateprojectfile/lookercreateprojectfile.go

@@ -16,14 +16,12 @@ package lookercreateprojectfile
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/looker/lookercommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 
 	"github.com/looker-open-source/sdk-codegen/go/rtl"
@@ -112,29 +110,29 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	sdk, err := source.GetLookerSDK(string(accessToken))
 	if err != nil {
-		return nil, util.NewClientServerError("error getting sdk", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting sdk: %w", err)
 	}
 
 	mapParams := params.AsMap()
 	projectId, ok := mapParams["project_id"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("'project_id' must be a string, got %T", mapParams["project_id"]), nil)
+		return nil, fmt.Errorf("'project_id' must be a string, got %T", mapParams["project_id"])
 	}
 	filePath, ok := mapParams["file_path"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("'file_path' must be a string, got %T", mapParams["file_path"]), nil)
+		return nil, fmt.Errorf("'file_path' must be a string, got %T", mapParams["file_path"])
 	}
 	fileContent, ok := mapParams["file_content"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("'file_content' must be a string, got %T", mapParams["file_content"]), nil)
+		return nil, fmt.Errorf("'file_content' must be a string, got %T", mapParams["file_content"])
 	}
 
 	req := lookercommon.FileContent{
@@ -144,7 +142,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 
 	err = lookercommon.CreateProjectFile(sdk, projectId, req, source.LookerApiSettings())
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, fmt.Errorf("error making create_project_file request: %s", err)
 	}
 
 	data := make(map[string]any)

internal/tools/looker/lookerdeleteprojectfile/lookerdeleteprojectfile.go

@@ -16,14 +16,12 @@ package lookerdeleteprojectfile
 import (
 	"context"
 	"fmt"
-	"net/http"
 
 	yaml "github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/embeddingmodels"
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/googleapis/genai-toolbox/internal/tools/looker/lookercommon"
-	"github.com/googleapis/genai-toolbox/internal/util"
 	"github.com/googleapis/genai-toolbox/internal/util/parameters"
 
 	"github.com/looker-open-source/sdk-codegen/go/rtl"
@@ -113,30 +111,30 @@ func (t Tool) ToConfig() tools.ToolConfig {
 	return t.Config
 }
 
-func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
+func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
 	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Type)
 	if err != nil {
-		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, err)
+		return nil, err
 	}
 
 	sdk, err := source.GetLookerSDK(string(accessToken))
 	if err != nil {
-		return nil, util.NewClientServerError("error getting sdk", http.StatusInternalServerError, err)
+		return nil, fmt.Errorf("error getting sdk: %w", err)
 	}
 
 	mapParams := params.AsMap()
 	projectId, ok := mapParams["project_id"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("'project_id' must be a string, got %T", mapParams["project_id"]), nil)
+		return nil, fmt.Errorf("'project_id' must be a string, got %T", mapParams["project_id"])
 	}
 	filePath, ok := mapParams["file_path"].(string)
 	if !ok {
-		return nil, util.NewAgentError(fmt.Sprintf("'file_path' must be a string, got %T", mapParams["file_path"]), nil)
+		return nil, fmt.Errorf("'file_path' must be a string, got %T", mapParams["file_path"])
 	}
 
 	err = lookercommon.DeleteProjectFile(sdk, projectId, filePath, source.LookerApiSettings())
 	if err != nil {
-		return nil, util.ProcessGeneralError(err)
+		return nil, fmt.Errorf("error making delete_project_file request: %s", err)
 	}
 
 	data := make(map[string]any)