Google Cloud MCP Server

Implementation Reference

• src/services/spanner/tools.ts:300-369 (handler)

  The main handler function for the 'list-spanner-databases' tool. It retrieves the project ID, creates a Spanner client, lists all databases in the specified instance, formats the results as a markdown table with state info, and includes resource URIs for further exploration (tables and schema).
  async ({ instanceId }, _extra) => { try { // First try to get the project ID from the state manager let projectId = stateManager.getCurrentProjectId(); if (!projectId) { // If not in state manager, try to get it from our function const authProjectId = await getProjectId(); if (authProjectId) { projectId = authProjectId; console.log(`Got project ID from getProjectId: ${projectId}`); } } else { console.log(`Got project ID from state manager: ${projectId}`); } if (!projectId) { throw new Error('Project ID could not be determined. Please set a project ID using the set-project-id tool.'); } // Create Spanner client with explicit project ID const spanner = new (await import('@google-cloud/spanner')).Spanner({ projectId: projectId }); console.log(`Using Spanner client with project ID: ${projectId} for list-spanner-databases`); const instance = spanner.instance(Array.isArray(instanceId) ? instanceId[0] : instanceId); const [databases] = await instance.getDatabases(); if (!databases || databases.length === 0) { return { content: [{ type: 'text', text: `# Spanner Databases\n\nProject: ${projectId}\nInstance: ${Array.isArray(instanceId) ? instanceId[0] : instanceId}\n\nNo databases found in the instance.` }] }; } let markdown = `# Spanner Databases\n\nProject: ${projectId}\nInstance: ${Array.isArray(instanceId) ? instanceId[0] : instanceId}\n\n`; // Table header markdown += '| Database ID | State |\n'; markdown += '|-------------|-------|\n'; // Table rows for (const database of databases) { const metadata = database.metadata || {}; markdown += `| ${database.id || 'unknown'} | ${metadata.state || 'unknown'} |\n`; } // Add resource links for further exploration markdown += '\n## Available Resources\n\n'; for (const database of databases) { markdown += `- Tables in ${database.id}: \`gcp-spanner://${projectId}/${Array.isArray(instanceId) ? instanceId[0] : instanceId}/${database.id}/tables\`\n`; markdown += `- Schema for ${database.id}: \`gcp-spanner://${projectId}/${Array.isArray(instanceId) ? instanceId[0] : instanceId}/${database.id}/schema\`\n`; } return { content: [{ type: 'text', text: markdown }] }; } catch (error: any) { console.error('Error listing Spanner databases:', error); throw error; } }
• src/services/spanner/tools.ts:297-299 (schema)

  Zod input schema for the tool, requiring a single 'instanceId' parameter as string.
  { instanceId: z.string().describe('Spanner instance ID') },
• src/services/spanner/tools.ts:295-370 (registration)

  Registers the 'list-spanner-databases' tool on the MCP server within the registerSpannerTools function.
  server.tool( 'list-spanner-databases', { instanceId: z.string().describe('Spanner instance ID') }, async ({ instanceId }, _extra) => { try { // First try to get the project ID from the state manager let projectId = stateManager.getCurrentProjectId(); if (!projectId) { // If not in state manager, try to get it from our function const authProjectId = await getProjectId(); if (authProjectId) { projectId = authProjectId; console.log(`Got project ID from getProjectId: ${projectId}`); } } else { console.log(`Got project ID from state manager: ${projectId}`); } if (!projectId) { throw new Error('Project ID could not be determined. Please set a project ID using the set-project-id tool.'); } // Create Spanner client with explicit project ID const spanner = new (await import('@google-cloud/spanner')).Spanner({ projectId: projectId }); console.log(`Using Spanner client with project ID: ${projectId} for list-spanner-databases`); const instance = spanner.instance(Array.isArray(instanceId) ? instanceId[0] : instanceId); const [databases] = await instance.getDatabases(); if (!databases || databases.length === 0) { return { content: [{ type: 'text', text: `# Spanner Databases\n\nProject: ${projectId}\nInstance: ${Array.isArray(instanceId) ? instanceId[0] : instanceId}\n\nNo databases found in the instance.` }] }; } let markdown = `# Spanner Databases\n\nProject: ${projectId}\nInstance: ${Array.isArray(instanceId) ? instanceId[0] : instanceId}\n\n`; // Table header markdown += '| Database ID | State |\n'; markdown += '|-------------|-------|\n'; // Table rows for (const database of databases) { const metadata = database.metadata || {}; markdown += `| ${database.id || 'unknown'} | ${metadata.state || 'unknown'} |\n`; } // Add resource links for further exploration markdown += '\n## Available Resources\n\n'; for (const database of databases) { markdown += `- Tables in ${database.id}: \`gcp-spanner://${projectId}/${Array.isArray(instanceId) ? instanceId[0] : instanceId}/${database.id}/tables\`\n`; markdown += `- Schema for ${database.id}: \`gcp-spanner://${projectId}/${Array.isArray(instanceId) ? instanceId[0] : instanceId}/${database.id}/schema\`\n`; } return { content: [{ type: 'text', text: markdown }] }; } catch (error: any) { console.error('Error listing Spanner databases:', error); throw error; } } );
• src/index.ts:139-142 (registration)

  Top-level server initialization calls registerSpannerTools(server), which includes the list-spanner-databases tool registration.
  registerSpannerResources(server); registerSpannerTools(server); registerSpannerQueryCountTool(server); } catch (error) {