feat(clickhouse): add list-databases tool (#1274)

## Description
---

Adds a tool to the list databases in a clickhouse cluster

<img width="1440" height="813" alt="Screenshot 2025-08-28 at 09 58 15"
src="https://github.com/user-attachments/assets/73643f5d-0c37-4e58-a81c-47bc3a2a5f8e"
/>


## 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/langchain-google-alloydb-pg-python/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] 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>

---------

Co-authored-by: Pete Hampton <pjhampton@users.noreply.github.com>
Co-authored-by: Averi Kitsch <akitsch@google.com>

cmd/root.go

@@ -54,6 +54,7 @@ import (
 	_ "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerysql"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/bigtable"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouseexecutesql"
+	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouselistdatabases"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhousesql"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudmonitoring"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/couchbase"

cmd/root_test.go

@@ -1369,7 +1369,7 @@ func TestPrebuiltTools(t *testing.T) {
 			wantToolset: server.ToolsetConfigs{
 				"clickhouse-database-tools": tools.ToolsetConfig{
 					Name:      "clickhouse-database-tools",
-					ToolNames: []string{"execute_sql"},
+					ToolNames: []string{"execute_sql", "list_databases"},
 				},
 			},
 		},

docs/en/resources/tools/clickhouse/clickhouse-list-databases.md

@@ -0,0 +1,53 @@
+---
+title: "clickhouse-list-databases"
+type: docs
+weight: 3
+description: >
+  A "clickhouse-list-databases" tool lists all databases in a ClickHouse instance.
+aliases:
+- /resources/tools/clickhouse-list-databases
+---
+
+## About
+
+A `clickhouse-list-databases` tool lists all available databases in a 
+ClickHouse instance. It's compatible with the [clickhouse](../../sources/clickhouse.md) source.
+
+This tool executes the `SHOW DATABASES` command and returns a list of all 
+databases accessible to the configured user, making it useful for database 
+discovery and exploration tasks.
+
+## Example
+
+```yaml
+tools:
+  list_clickhouse_databases:
+    kind: clickhouse-list-databases
+    source: my-clickhouse-instance
+    description: List all available databases in the ClickHouse instance
+```
+
+## Return Value
+
+The tool returns an array of objects, where each object contains:
+- `name`: The name of the database
+
+Example response:
+```json
+[
+  {"name": "default"},
+  {"name": "system"},
+  {"name": "analytics"},
+  {"name": "user_data"}
+]
+```
+
+## Reference
+
+| **field**          | **type**           | **required** | **description**                                           |
+|--------------------|:------------------:|:------------:|-----------------------------------------------------------|
+| kind               | string             | true         | Must be "clickhouse-list-databases".                     |
+| source             | string             | true         | Name of the ClickHouse source to list databases from.    |
+| description        | string             | true         | Description of the tool that is passed to the LLM.       |
+| authRequired       | array of string    | false        | Authentication services required to use this tool.       |
+| parameters         | array of Parameter | false        | Parameters for the tool (typically not used).            |

internal/prebuiltconfigs/tools/clickhouse.yaml

@@ -1,3 +1,16 @@
+# 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.
 sources:
   clickhouse-source:
     kind: clickhouse
@@ -14,6 +27,12 @@ tools:
     source: clickhouse-source
     description: Use this tool to execute SQL.
 
+  list_databases:
+    kind: clickhouse-list-databases
+    source: clickhouse-source
+    description: Use this tool to list all databases in ClickHouse.
+
 toolsets:
   clickhouse-database-tools:
     - execute_sql
+    - list_databases

internal/tools/clickhouse/clickhouselistdatabases/clickhouselistdatabases.go

@@ -0,0 +1,157 @@
+// 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 clickhouse
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	yaml "github.com/goccy/go-yaml"
+	"github.com/googleapis/genai-toolbox/internal/sources"
+	"github.com/googleapis/genai-toolbox/internal/tools"
+)
+
+type compatibleSource interface {
+	ClickHousePool() *sql.DB
+}
+
+var compatibleSources = []string{"clickhouse"}
+
+const listDatabasesKind string = "clickhouse-list-databases"
+
+func init() {
+	if !tools.Register(listDatabasesKind, newListDatabasesConfig) {
+		panic(fmt.Sprintf("tool kind %q already registered", listDatabasesKind))
+	}
+}
+
+func newListDatabasesConfig(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
+}
+
+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" validate:"required"`
+	AuthRequired []string         `yaml:"authRequired"`
+	Parameters   tools.Parameters `yaml:"parameters"`
+}
+
+var _ tools.ToolConfig = Config{}
+
+func (cfg Config) ToolConfigKind() string {
+	return listDatabasesKind
+}
+
+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.(compatibleSource)
+	if !ok {
+		return nil, fmt.Errorf("invalid source for %q tool: source kind must be one of %q", listDatabasesKind, compatibleSources)
+	}
+
+	allParameters, paramManifest, paramMcpManifest, _ := tools.ProcessParameters(nil, cfg.Parameters)
+
+	mcpManifest := tools.McpManifest{
+		Name:        cfg.Name,
+		Description: cfg.Description,
+		InputSchema: paramMcpManifest,
+	}
+
+	t := Tool{
+		Name:         cfg.Name,
+		Kind:         listDatabasesKind,
+		Parameters:   cfg.Parameters,
+		AllParams:    allParameters,
+		AuthRequired: cfg.AuthRequired,
+		Pool:         s.ClickHousePool(),
+		manifest:     tools.Manifest{Description: cfg.Description, Parameters: paramManifest, AuthRequired: cfg.AuthRequired},
+		mcpManifest:  mcpManifest,
+	}
+	return t, nil
+}
+
+var _ tools.Tool = Tool{}
+
+type Tool struct {
+	Name         string           `yaml:"name"`
+	Kind         string           `yaml:"kind"`
+	AuthRequired []string         `yaml:"authRequired"`
+	Parameters   tools.Parameters `yaml:"parameters"`
+	AllParams    tools.Parameters `yaml:"allParams"`
+
+	Pool        *sql.DB
+	manifest    tools.Manifest
+	mcpManifest tools.McpManifest
+}
+
+func (t Tool) Invoke(ctx context.Context, params tools.ParamValues, token tools.AccessToken) (any, error) {
+	// Query to list all databases
+	query := "SHOW DATABASES"
+
+	results, err := t.Pool.QueryContext(ctx, query)
+	if err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+	defer results.Close()
+
+	var databases []map[string]any
+	for results.Next() {
+		var dbName string
+		err := results.Scan(&dbName)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse row: %w", err)
+		}
+		databases = append(databases, map[string]any{
+			"name": dbName,
+		})
+	}
+
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("errors encountered by results.Scan: %w", err)
+	}
+
+	return databases, nil
+}
+
+func (t Tool) ParseParams(data map[string]any, claims map[string]map[string]any) (tools.ParamValues, error) {
+	return tools.ParseParams(t.AllParams, data, claims)
+}
+
+func (t Tool) Manifest() tools.Manifest {
+	return t.manifest
+}
+
+func (t Tool) McpManifest() tools.McpManifest {
+	return t.mcpManifest
+}
+
+func (t Tool) Authorized(verifiedAuthServices []string) bool {
+	return tools.IsAuthorized(t.AuthRequired, verifiedAuthServices)
+}
+
+func (t Tool) RequiresClientAuthorization() bool {
+	return false
+}

internal/tools/clickhouse/clickhouselistdatabases/clickhouselistdatabases_test.go

@@ -0,0 +1,109 @@
+// 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 clickhouse
+
+import (
+	"testing"
+
+	yaml "github.com/goccy/go-yaml"
+	"github.com/google/go-cmp/cmp"
+	"github.com/googleapis/genai-toolbox/internal/server"
+	"github.com/googleapis/genai-toolbox/internal/sources"
+	"github.com/googleapis/genai-toolbox/internal/testutils"
+	"github.com/googleapis/genai-toolbox/internal/tools"
+)
+
+func TestListDatabasesConfigToolConfigKind(t *testing.T) {
+	cfg := Config{}
+	if cfg.ToolConfigKind() != listDatabasesKind {
+		t.Errorf("expected %q, got %q", listDatabasesKind, cfg.ToolConfigKind())
+	}
+}
+
+func TestListDatabasesConfigInitializeMissingSource(t *testing.T) {
+	cfg := Config{
+		Name:        "test-list-databases",
+		Kind:        listDatabasesKind,
+		Source:      "missing-source",
+		Description: "Test list databases tool",
+	}
+
+	srcs := map[string]sources.Source{}
+	_, err := cfg.Initialize(srcs)
+	if err == nil {
+		t.Error("expected error for missing source")
+	}
+}
+
+func TestParseFromYamlClickHouseListDatabases(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:
+				example_tool:
+					kind: clickhouse-list-databases
+					source: my-instance
+					description: some description
+			`,
+			want: server.ToolConfigs{
+				"example_tool": Config{
+					Name:         "example_tool",
+					Kind:         "clickhouse-list-databases",
+					Source:       "my-instance",
+					Description:  "some description",
+					AuthRequired: []string{},
+				},
+			},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			got := struct {
+				Tools server.ToolConfigs `yaml:"tools"`
+			}{}
+			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)
+			}
+		})
+	}
+}
+
+func TestListDatabasesToolParseParams(t *testing.T) {
+	tool := Tool{
+		Parameters: tools.Parameters{},
+	}
+
+	params, err := tool.ParseParams(map[string]any{}, map[string]map[string]any{})
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+
+	if len(params) != 0 {
+		t.Errorf("expected 0 parameters, got %d", len(params))
+	}
+}

tests/clickhouse/clickhouse_integration_test.go

@@ -31,6 +31,7 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/testutils"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	clickhouseexecutesql "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouseexecutesql"
+	clickhouselistdatabases "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouselistdatabases"
 	clickhousesql "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhousesql"
 	"github.com/googleapis/genai-toolbox/tests"
 	"go.opentelemetry.io/otel/trace/noop"
@@ -1012,3 +1013,103 @@ func setupClickHouseSQLTable(t *testing.T, ctx context.Context, pool *sql.DB, cr
 		}
 	}
 }
+
+func TestClickHouseListDatabasesTool(t *testing.T) {
+	_ = getClickHouseVars(t)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+
+	pool, err := initClickHouseConnectionPool(ClickHouseHost, ClickHousePort, ClickHouseUser, ClickHousePass, ClickHouseDatabase, ClickHouseProtocol)
+	if err != nil {
+		t.Fatalf("unable to create ClickHouse connection pool: %s", err)
+	}
+	defer pool.Close()
+
+	// Create a test database
+	testDBName := "test_list_db_" + strings.ReplaceAll(uuid.New().String(), "-", "")[:8]
+	_, err = pool.ExecContext(ctx, fmt.Sprintf("CREATE DATABASE IF NOT EXISTS %s", testDBName))
+	if err != nil {
+		t.Fatalf("Failed to create test database: %v", err)
+	}
+	defer func() {
+		_, _ = pool.ExecContext(ctx, fmt.Sprintf("DROP DATABASE IF EXISTS %s", testDBName))
+	}()
+
+	t.Run("ListDatabases", func(t *testing.T) {
+		toolConfig := clickhouselistdatabases.Config{
+			Name:        "test-list-databases",
+			Kind:        "clickhouse-list-databases",
+			Source:      "test-clickhouse",
+			Description: "Test listing databases",
+		}
+
+		source := createMockSource(t, pool)
+		sourcesMap := map[string]sources.Source{
+			"test-clickhouse": source,
+		}
+
+		tool, err := toolConfig.Initialize(sourcesMap)
+		if err != nil {
+			t.Fatalf("Failed to initialize tool: %v", err)
+		}
+
+		params := tools.ParamValues{}
+
+		result, err := tool.Invoke(ctx, params, "")
+		if err != nil {
+			t.Fatalf("Failed to list databases: %v", err)
+		}
+
+		databases, ok := result.([]map[string]any)
+		if !ok {
+			t.Fatalf("Expected result to be []map[string]any, got %T", result)
+		}
+
+		// Should contain at least the default database and our test database - system and default
+		if len(databases) < 2 {
+			t.Errorf("Expected at least 2 databases, got %d", len(databases))
+		}
+
+		found := false
+		foundDefault := false
+		for _, db := range databases {
+			if name, ok := db["name"].(string); ok {
+				if name == testDBName {
+					found = true
+				}
+				if name == "default" || name == "system" {
+					foundDefault = true
+				}
+			}
+		}
+
+		if !found {
+			t.Errorf("Test database %s not found in list", testDBName)
+		}
+		if !foundDefault {
+			t.Errorf("Default/system database not found in list")
+		}
+
+		t.Logf("Successfully listed %d databases", len(databases))
+	})
+
+	t.Run("ListDatabasesWithInvalidSource", func(t *testing.T) {
+		toolConfig := clickhouselistdatabases.Config{
+			Name:        "test-invalid-source",
+			Kind:        "clickhouse-list-databases",
+			Source:      "non-existent-source",
+			Description: "Test with invalid source",
+		}
+
+		sourcesMap := map[string]sources.Source{}
+
+		_, err := toolConfig.Initialize(sourcesMap)
+		if err == nil {
+			t.Error("Expected error for non-existent source, got nil")
+		} else {
+			t.Logf("Got expected error for invalid source: %v", err)
+		}
+	})
+
+	t.Logf("✅ clickhouse-list-databases tool tests completed successfully")
+}