refactor error return

internal/server/api.go

@@ -234,8 +234,13 @@ 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
-		if errors.Is(err, util.ErrUnauthorized) {
-			s.logger.DebugContext(ctx, fmt.Sprintf("error parsing authenticated parameters from ID token: %s", err))
+		errMsg := fmt.Sprintf("error parsing authenticated parameters from ID token: %w", err)
+		if errors.Is(err, util.NewClientServerError(
+			errMsg,
+			http.StatusUnauthorized,
+			nil,
+		)) {
+			s.logger.DebugContext(ctx, errMsg)
 			_ = render.Render(w, r, newErrResponse(err, http.StatusUnauthorized))
 			return
 		}
@@ -270,12 +275,12 @@ func toolInvokeHandler(s *Server, w http.ResponseWriter, r *http.Request) {
 
 			case util.CategoryServer:
 				// Server Errors -> Check the specific code inside
-				var serverErr *util.ServerError
+				var clientServerErr *util.ClientServerError
 				statusCode := http.StatusInternalServerError // Default to 500
 
-				if errors.As(err, &serverErr) {
-					if serverErr.Code != 0 {
-						statusCode = serverErr.Code
+				if errors.As(err, &clientServerErr) {
+					if clientServerErr.Code != 0 {
+						statusCode = clientServerErr.Code
 					}
 				}
 

internal/server/mcp.go

@@ -23,7 +23,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"strings"
 	"sync"
 	"time"
 
@@ -444,15 +443,17 @@ 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:
-			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)
+			var clientServerErr *util.ClientServerError
+			if errors.As(err, &clientServerErr) {
+				switch clientServerErr.Code {
+				case http.StatusUnauthorized:
+					w.WriteHeader(http.StatusUnauthorized)
+				case http.StatusForbidden:
+					w.WriteHeader(http.StatusForbidden)
+				}
 			}
 		}
 	}

internal/server/mcp/v20241105/method.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
-	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -124,7 +123,11 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.NewClientServerError(
+				"missing access token in the 'Authorization' header",
+				http.StatusUnauthorized,
+				nil,
+			)
 		}
 	}
 
@@ -172,8 +175,11 @@ 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 = 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
+		err = util.NewClientServerError(
+			"unauthorized Tool call: Please make sure you specify correct auth headers",
+			http.StatusUnauthorized,
+			nil,
+		)
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
 
@@ -194,30 +200,41 @@ 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 {
-		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
-			}
-			// Auth error with ADC should raise internal 500 error
-			return jsonrpc.NewError(id, jsonrpc.INTERNAL_ERROR, err.Error(), nil), err
-		}
+		var tbErr util.ToolboxError
 
-		text := TextContent{
-			Type: "text",
-			Text: err.Error(),
+		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
+			}
 		}
-		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

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
-	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -124,7 +123,11 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.NewClientServerError(
+				"missing access token in the 'Authorization' header",
+				http.StatusUnauthorized,
+				nil,
+			)
 		}
 	}
 
@@ -172,8 +175,11 @@ 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 = 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
+		err = util.NewClientServerError(
+			"unauthorized Tool call: Please make sure you specify correct auth headers",
+			http.StatusUnauthorized,
+			nil,
+		)
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
 
@@ -194,31 +200,42 @@ 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 {
-		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
-			}
-			// 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
-	}
+		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
+			}
+		}
+	}
 	content := make([]TextContent, 0)
 
 	sliceRes, ok := results.([]any)

internal/server/mcp/v20250618/method.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
-	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -117,7 +116,12 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
+			errMsg := "missing access token in the 'Authorization' header"
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, errMsg, nil), util.NewClientServerError(
+				errMsg,
+				http.StatusUnauthorized,
+				nil,
+			)
 		}
 	}
 
@@ -165,8 +169,11 @@ 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 = 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
+		err = util.NewClientServerError(
+			"unauthorized Tool call: Please make sure you specify correct auth headers",
+			http.StatusUnauthorized,
+			nil,
+		)
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
 
@@ -187,29 +194,41 @@ 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 {
-		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
+		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
 			}
-			// 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

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
-	"strings"
 
 	"github.com/googleapis/genai-toolbox/internal/prompts"
 	"github.com/googleapis/genai-toolbox/internal/server/mcp/jsonrpc"
@@ -117,7 +116,11 @@ func toolsCallHandler(ctx context.Context, id jsonrpc.RequestId, resourceMgr *re
 	}
 	if clientAuth {
 		if accessToken == "" {
-			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.ErrUnauthorized
+			return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, "missing access token in the 'Authorization' header", nil), util.NewClientServerError(
+				"missing access token in the 'Authorization' header",
+				http.StatusUnauthorized,
+				nil,
+			)
 		}
 	}
 
@@ -165,7 +168,11 @@ 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 = fmt.Errorf("unauthorized Tool call: Please make sure your specify correct auth headers: %w", util.ErrUnauthorized)
+		err = util.NewClientServerError(
+			"unauthorized Tool call: Please make sure you specify correct auth headers",
+			http.StatusUnauthorized,
+			nil,
+		)
 		return jsonrpc.NewError(id, jsonrpc.INVALID_REQUEST, err.Error(), nil), err
 	}
 	logger.DebugContext(ctx, "tool invocation authorized")
@@ -187,29 +194,41 @@ 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 {
-		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
+		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
 			}
-			// 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/tools/bigquery/bigqueryconversationalanalytics/bigqueryconversationalanalytics.go

@@ -184,7 +184,7 @@ func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, para
 	if source.UseClientAuthorization() {
 		// Use client-side access token
 		if accessToken == "" {
-			return nil, fmt.Errorf("tool is configured for client OAuth but no token was provided in the request header: %w", util.ErrUnauthorized)
+			return nil, util.NewClientServerError("tool is configured for client OAuth but no token was provided in the request header", http.StatusUnauthorized, nil)
 		}
 		tokenStr, err = accessToken.ParseBearerToken()
 		if err != nil {

internal/tools/tools.go

@@ -17,6 +17,7 @@ package tools
 import (
 	"context"
 	"fmt"
+	"net/http"
 	"slices"
 	"strings"
 
@@ -80,7 +81,7 @@ type AccessToken string
 func (token AccessToken) ParseBearerToken() (string, error) {
 	headerParts := strings.Split(string(token), " ")
 	if len(headerParts) != 2 || strings.ToLower(headerParts[0]) != "bearer" {
-		return "", fmt.Errorf("authorization header must be in the format 'Bearer <token>': %w", util.ErrUnauthorized)
+		return "", util.NewClientServerError("authorization header must be in the format 'Bearer <token>'", http.StatusUnauthorized, nil)
 	}
 	return headerParts[1], nil
 }

internal/util/parameters/parameters.go

@@ -19,6 +19,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"reflect"
 	"regexp"
 	"slices"
@@ -118,7 +119,7 @@ func parseFromAuthService(paramAuthServices []ParamAuthService, claimsMap map[st
 		}
 		return v, nil
 	}
-	return nil, fmt.Errorf("missing or invalid authentication header: %w", util.ErrUnauthorized)
+	return nil, util.NewClientServerError("missing or invalid authentication header", http.StatusUnauthorized, nil)
 }
 
 // CheckParamRequired checks if a parameter is required based on the required and default field.

internal/util/util.go

@@ -17,7 +17,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -188,5 +187,3 @@ func InstrumentationFromContext(ctx context.Context) (*telemetry.Instrumentation
 	}
 	return nil, fmt.Errorf("unable to retrieve instrumentation")
 }
-
-var ErrUnauthorized = errors.New("unauthorized")