feat(prebuilt/cloudsql): Add list databases tool for cloud sql (#1454)

## Description

---
feat: Add tool to list Cloud SQL databases

This change introduces a new tool for listing databases within a Google
Cloud SQL instance.

The new tool, `list-databases`, is part of the `cloud-sql-admin` source
and allows users to retrieve a list of all databases for a given
instance.

### Detailed Description

The `list-databases` tool provides a simple and direct way to inspect
the databases present in a Cloud SQL instance. It is implemented in
`internal/tools/cloudsql/cloudsqllistdatabases/cloudsqllistdatabases.go`.

**Key Features:**

*   **Tool Name:** `list-databases`
*   **Source:** `cloud-sql-admin`
*   **Parameters:**
    *   `project` (required): The Google Cloud project ID.
    *   `instance` (required): The ID of the Cloud SQL instance.
*   **Functionality:**
* The tool uses the `sqladmin.Databases.List` API to fetch the list of
databases.
* It formats the output into a JSON array, where each object contains
the `name`, `charset`, and `collation` of a database.
    *   If no databases are found, it returns an empty array.


## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #<issue_number_goes_here>

cmd/root.go

@@ -66,6 +66,7 @@ import (
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqlcreatedatabase"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqlcreateusers"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqlgetinstances"
+	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqllistdatabases"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqllistinstances"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqlwaitforoperation"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudsqlmssql/cloudsqlmssqlcreateinstance"

docs/en/resources/tools/cloudsql/cloudsqllistdatabases.md

@@ -0,0 +1,47 @@
+---
+title: cloud-sql-list-databases
+type: docs
+weight: 1
+description: List Cloud SQL databases in an instance.
+---
+
+The `cloud-sql-list-databases` tool lists all Cloud SQL databases in a specified
+Google Cloud project and instance.
+
+{{< notice info >}}
+This tool uses the `cloud-sql-admin` source.
+{{< /notice >}}
+
+## Configuration
+
+Here is an example of how to configure the `cloud-sql-list-databases` tool in your
+`tools.yaml` file:
+
+```yaml
+sources:
+  my-cloud-sql-admin-source:
+    kind: cloud-sql-admin
+
+tools:
+  list_my_databases:
+    kind: cloud-sql-list-databases
+    source: my-cloud-sql-admin-source
+    description: Use this tool to list all Cloud SQL databases in an instance.
+```
+
+## Parameters
+
+The `cloud-sql-list-databases` tool has two required parameters:
+
+| **field** | **type** | **required** | **description**              |
+| --------- | :------: | :----------: | ---------------------------- |
+| project   |  string  |     true     | The Google Cloud project ID. |
+| instance  |  string  |     true     | The Cloud SQL instance ID.   |
+
+## Reference
+
+| **field**   | **type** | **required** | **description**                                                |
+| ----------- | :------: | :----------: | -------------------------------------------------------------- |
+| kind        |  string  |     true     | Must be "cloud-sql-list-databases".                            |
+| source      |  string  |     true     | The name of the `cloud-sql-admin` source to use for this tool. |
+| description |  string  |     false    | Description of the tool that is passed to the agent.           |

internal/tools/cloudsql/cloudsqllistdatabases/cloudsqllistdatabases.go

@@ -0,0 +1,182 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cloudsqllistdatabases
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/goccy/go-yaml"
+	"github.com/googleapis/genai-toolbox/internal/sources"
+	cloudsqladminsrc "github.com/googleapis/genai-toolbox/internal/sources/cloudsqladmin"
+	"github.com/googleapis/genai-toolbox/internal/tools"
+)
+
+const kind string = "cloud-sql-list-databases"
+
+func init() {
+	if !tools.Register(kind, newConfig) {
+		panic(fmt.Sprintf("tool kind %q already registered", kind))
+	}
+}
+
+func newConfig(ctx context.Context, name string, decoder *yaml.Decoder) (tools.ToolConfig, error) {
+	actual := Config{Name: name}
+	if err := decoder.DecodeContext(ctx, &actual); err != nil {
+		return nil, err
+	}
+	return actual, nil
+}
+
+// Config defines the configuration for the list-databases tool.
+type Config struct {
+	Name         string   `yaml:"name" validate:"required"`
+	Kind         string   `yaml:"kind" validate:"required"`
+	Source       string   `yaml:"source" validate:"required"`
+	Description  string   `yaml:"description"`
+	AuthRequired []string `yaml:"authRequired"`
+}
+
+// validate interface
+var _ tools.ToolConfig = Config{}
+
+// ToolConfigKind returns the kind of the tool.
+func (cfg Config) ToolConfigKind() string {
+	return kind
+}
+
+// Initialize initializes the tool from the configuration.
+func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error) {
+	rawS, ok := srcs[cfg.Source]
+	if !ok {
+		return nil, fmt.Errorf("no source named %q configured", cfg.Source)
+	}
+	s, ok := rawS.(*cloudsqladminsrc.Source)
+	if !ok {
+		return nil, fmt.Errorf("invalid source for %q tool: source kind must be `cloud-sql-admin`", kind)
+	}
+
+	allParameters := tools.Parameters{
+		tools.NewStringParameter("project", "The project ID"),
+		tools.NewStringParameter("instance", "The instance ID"),
+	}
+	paramManifest := allParameters.Manifest()
+
+	inputSchema := allParameters.McpManifest()
+	inputSchema.Required = []string{"project", "instance"}
+
+	description := cfg.Description
+	if description == "" {
+		description = "Lists all databases for a Cloud SQL instance."
+	}
+
+	mcpManifest := tools.McpManifest{
+		Name:        cfg.Name,
+		Description: description,
+		InputSchema: inputSchema,
+	}
+
+	return Tool{
+		Name:         cfg.Name,
+		Kind:         kind,
+		AuthRequired: cfg.AuthRequired,
+		Source:       s,
+		AllParams:    allParameters,
+		manifest:     tools.Manifest{Description: description, Parameters: paramManifest, AuthRequired: cfg.AuthRequired},
+		mcpManifest:  mcpManifest,
+	}, nil
+}
+
+// Tool represents the list-databases tool.
+type Tool struct {
+	Name         string   `yaml:"name"`
+	Kind         string   `yaml:"kind"`
+	Description  string   `yaml:"description"`
+	AuthRequired []string `yaml:"authRequired"`
+
+	AllParams   tools.Parameters `yaml:"allParams"`
+	Source      *cloudsqladminsrc.Source
+	manifest    tools.Manifest
+	mcpManifest tools.McpManifest
+}
+
+// Invoke executes the tool's logic.
+func (t Tool) Invoke(ctx context.Context, params tools.ParamValues, accessToken tools.AccessToken) (any, error) {
+	paramsMap := params.AsMap()
+
+	project, ok := paramsMap["project"].(string)
+	if !ok {
+		return nil, fmt.Errorf("missing 'project' parameter")
+	}
+	instance, ok := paramsMap["instance"].(string)
+	if !ok {
+		return nil, fmt.Errorf("missing 'instance' parameter")
+	}
+
+	service, err := t.Source.GetService(ctx, string(accessToken))
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := service.Databases.List(project, instance).Do()
+	if err != nil {
+		return nil, fmt.Errorf("error listing databases: %w", err)
+	}
+
+	if resp.Items == nil {
+		return []any{}, nil
+	}
+
+	type databaseInfo struct {
+		Name      string `json:"name"`
+		Charset   string `json:"charset"`
+		Collation string `json:"collation"`
+	}
+
+	var databases []databaseInfo
+	for _, item := range resp.Items {
+		databases = append(databases, databaseInfo{
+			Name:      item.Name,
+			Charset:   item.Charset,
+			Collation: item.Collation,
+		})
+	}
+
+	return databases, nil
+}
+
+// ParseParams parses the parameters for the tool.
+func (t Tool) ParseParams(data map[string]any, claims map[string]map[string]any) (tools.ParamValues, error) {
+	return tools.ParseParams(t.AllParams, data, claims)
+}
+
+// Manifest returns the tool's manifest.
+func (t Tool) Manifest() tools.Manifest {
+	return t.manifest
+}
+
+// McpManifest returns the tool's MCP manifest.
+func (t Tool) McpManifest() tools.McpManifest {
+	return t.mcpManifest
+}
+
+// Authorized checks if the tool is authorized.
+func (t Tool) Authorized(verifiedAuthServices []string) bool {
+	return true
+}
+
+func (t Tool) RequiresClientAuthorization() bool {
+	return t.Source.UseClientAuthorization()
+}

internal/tools/cloudsql/cloudsqllistdatabases/cloudsqllistdatabases_test.go

@@ -0,0 +1,72 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cloudsqllistdatabases_test
+
+import (
+	"testing"
+
+	"github.com/goccy/go-yaml"
+	"github.com/google/go-cmp/cmp"
+	"github.com/googleapis/genai-toolbox/internal/server"
+	"github.com/googleapis/genai-toolbox/internal/testutils"
+	"github.com/googleapis/genai-toolbox/internal/tools/cloudsql/cloudsqllistdatabases"
+)
+
+func TestParseFromYaml(t *testing.T) {
+	ctx, err := testutils.ContextWithNewLogger()
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	tcs := []struct {
+		desc string
+		in   string
+		want server.ToolConfigs
+	}{
+		{
+			desc: "basic example",
+			in: `
+			tools:
+				list-my-databases:
+					kind: cloud-sql-list-databases
+					description: some description
+					source: some-source
+			`,
+			want: server.ToolConfigs{
+				"list-my-databases": cloudsqllistdatabases.Config{
+					Name:         "list-my-databases",
+					Kind:         "cloud-sql-list-databases",
+					Description:  "some description",
+					AuthRequired: []string{},
+					Source:       "some-source",
+				},
+			},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			got := struct {
+				Tools server.ToolConfigs `yaml:"tools"`
+			}{}
+			// Parse contents
+			err := yaml.UnmarshalContext(ctx, testutils.FormatYaml(tc.in), &got)
+			if err != nil {
+				t.Fatalf("unable to unmarshal: %s", err)
+			}
+			if diff := cmp.Diff(tc.want, got.Tools); diff != "" {
+				t.Fatalf("incorrect parse: diff %v", diff)
+			}
+		})
+	}
+}

tests/cloudsql/cloud_sql_list_databases_test.go

@@ -0,0 +1,213 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cloudsql
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"reflect"
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/googleapis/genai-toolbox/internal/testutils"
+	"github.com/googleapis/genai-toolbox/tests"
+)
+
+var (
+	listDatabasesToolKind = "cloud-sql-list-databases"
+)
+
+type listDatabasesTransport struct {
+	transport http.RoundTripper
+	url       *url.URL
+}
+
+func (t *listDatabasesTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	if strings.HasPrefix(req.URL.String(), "https://sqladmin.googleapis.com") {
+		req.URL.Scheme = t.url.Scheme
+		req.URL.Host = t.url.Host
+	}
+	return t.transport.RoundTrip(req)
+}
+
+type masterListDatabasesHandler struct {
+	t *testing.T
+}
+
+func (h *masterListDatabasesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if !strings.Contains(r.UserAgent(), "genai-toolbox/") {
+		h.t.Errorf("User-Agent header not found")
+	}
+
+	response := map[string]any{
+		"items": []map[string]any{
+			{
+				"name":      "db1",
+				"charset":   "utf8",
+				"collation": "utf8_general_ci",
+			},
+			{
+				"name":      "db2",
+				"charset":   "utf8mb4",
+				"collation": "utf8mb4_unicode_ci",
+			},
+		},
+	}
+	statusCode := http.StatusOK
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(statusCode)
+	if err := json.NewEncoder(w).Encode(response); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+	}
+}
+
+func TestListDatabasesToolEndpoints(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+
+	handler := &masterListDatabasesHandler{t: t}
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	serverURL, err := url.Parse(server.URL)
+	if err != nil {
+		t.Fatalf("failed to parse server URL: %v", err)
+	}
+
+	originalTransport := http.DefaultClient.Transport
+	if originalTransport == nil {
+		originalTransport = http.DefaultTransport
+	}
+	http.DefaultClient.Transport = &listDatabasesTransport{
+		transport: originalTransport,
+		url:       serverURL,
+	}
+	t.Cleanup(func() {
+		http.DefaultClient.Transport = originalTransport
+	})
+
+	var args []string
+	toolsFile := getListDatabasesToolsConfig()
+	cmd, cleanup, err := tests.StartCmd(ctx, toolsFile, args...)
+	if err != nil {
+		t.Fatalf("command initialization returned an error: %s", err)
+	}
+	defer cleanup()
+
+	waitCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+	out, err := testutils.WaitForString(waitCtx, regexp.MustCompile(`Server ready to serve`), cmd.Out)
+	if err != nil {
+		t.Logf("toolbox command logs: \n%s", out)
+		t.Fatalf("toolbox didn't start successfully: %s", err)
+	}
+
+	tcs := []struct {
+		name        string
+		toolName    string
+		body        string
+		want        string
+		expectError bool
+		errorStatus int
+	}{
+		{
+			name:     "successful databases listing",
+			toolName: "list-databases",
+			body:     `{"project": "p1", "instance": "i1"}`,
+			want:     `[{"name":"db1","charset":"utf8","collation":"utf8_general_ci"},{"name":"db2","charset":"utf8mb4","collation":"utf8mb4_unicode_ci"}]`,
+		},
+		{
+			name:        "missing instance",
+			toolName:    "list-databases",
+			body:        `{"project": "p1"}`,
+			expectError: true,
+			errorStatus: http.StatusBadRequest,
+		},
+	}
+
+	for _, tc := range tcs {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			api := fmt.Sprintf("http://127.0.0.1:5000/api/tool/%s/invoke", tc.toolName)
+			req, err := http.NewRequest(http.MethodPost, api, bytes.NewBufferString(tc.body))
+			if err != nil {
+				t.Fatalf("unable to create request: %s", err)
+			}
+			req.Header.Add("Content-type", "application/json")
+			resp, err := http.DefaultClient.Do(req)
+			if err != nil {
+				t.Fatalf("unable to send request: %s", err)
+			}
+			defer resp.Body.Close()
+
+			if tc.expectError {
+				if resp.StatusCode != tc.errorStatus {
+					bodyBytes, _ := io.ReadAll(resp.Body)
+					t.Fatalf("expected status %d but got %d: %s", tc.errorStatus, resp.StatusCode, string(bodyBytes))
+				}
+				return
+			}
+
+			if resp.StatusCode != http.StatusOK {
+				bodyBytes, _ := io.ReadAll(resp.Body)
+				t.Fatalf("response status code is not 200, got %d: %s", resp.StatusCode, string(bodyBytes))
+			}
+
+			var result struct {
+				Result string `json:"result"`
+			}
+			if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+				t.Fatalf("failed to decode response: %v", err)
+			}
+
+			var got, want []map[string]any
+			if err := json.Unmarshal([]byte(result.Result), &got); err != nil {
+				t.Fatalf("failed to unmarshal result: %v", err)
+			}
+			if err := json.Unmarshal([]byte(tc.want), &want); err != nil {
+				t.Fatalf("failed to unmarshal want: %v", err)
+			}
+
+			if !reflect.DeepEqual(got, want) {
+				t.Fatalf("unexpected result: got %+v, want %+v", got, want)
+			}
+		})
+	}
+}
+
+func getListDatabasesToolsConfig() map[string]any {
+	return map[string]any{
+		"sources": map[string]any{
+			"my-cloud-sql-source": map[string]any{
+				"kind": "cloud-sql-admin",
+			},
+		},
+		"tools": map[string]any{
+			"list-databases": map[string]any{
+				"kind":   listDatabasesToolKind,
+				"source": "my-cloud-sql-source",
+			},
+		},
+	}
+}