Google Cloud MCP Server

Implementation Reference

• src/services/spanner/tools.ts:255-339 (handler)

  The handler function that implements the core logic of the 'gcp-spanner-list-instances' tool. It determines the GCP project ID from state manager, environment, or auth; creates a Spanner client; lists all instances using spanner.getInstances(); and returns a formatted markdown response including a table of instances (ID, state, config, nodes) and resource links for further exploration.
  async (_params, _extra) => { try { // First try to get the project ID from the state manager let projectId = stateManager.getCurrentProjectId(); if (projectId) { logger.debug(`Got project ID from state manager: ${projectId}`); } else { // If not in state manager, try to get it from environment const envProjectId = process.env.GOOGLE_CLOUD_PROJECT; if (envProjectId) { projectId = envProjectId; logger.debug(`Got project ID from environment: ${projectId}`); // Store in state manager for future use await stateManager.setCurrentProjectId(projectId); } else { // If not in environment, try to get it from our function projectId = await getProjectId(); logger.debug(`Got project ID from getProjectId: ${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, }); logger.debug( `Using Spanner client with explicit project ID: ${projectId} for list-spanner-instances`, ); const [instances] = await spanner.getInstances(); if (!instances || instances.length === 0) { return { content: [ { type: "text", text: `# Spanner Instances\n\nProject: ${projectId}\n\nNo instances found in the project.`, }, ], }; } let markdown = `# Spanner Instances\n\nProject: ${projectId}\n\n`; // Table header markdown += "| Instance ID | State | Config | Nodes |\n"; markdown += "|-------------|-------|--------|-------|\n"; // Table rows for (const instance of instances) { const metadata = instance.metadata || {}; markdown += `| ${instance.id || "unknown"} | ${metadata.state || "unknown"} | ${metadata.config?.split("/").pop() || "unknown"} | ${metadata.nodeCount || "unknown"} |\n`; } // Add resource links for further exploration markdown += "\n## Available Resources\n\n"; markdown += `- All Instances: \`gcp-spanner://${projectId}/instances\`\n`; for (const instance of instances) { markdown += `- Databases in ${instance.id}: \`gcp-spanner://${projectId}/${instance.id}/databases\`\n`; } return { content: [ { type: "text", text: markdown, }, ], }; } catch (error: any) { logger.error( `Error listing Spanner instances: ${error instanceof Error ? error.message : String(error)}`, ); throw error; }
• src/services/spanner/tools.ts:245-341 (registration)

  The server.tool registration for 'gcp-spanner-list-instances', defining the tool name, input schema (minimal dummy param for compatibility), and inline handler function.
  server.tool( "gcp-spanner-list-instances", // Define an empty schema with a dummy parameter that's optional // This ensures compatibility with clients that expect an object parameter { _dummy: z .string() .optional() .describe("Not used, just to ensure parameter compatibility"), }, async (_params, _extra) => { try { // First try to get the project ID from the state manager let projectId = stateManager.getCurrentProjectId(); if (projectId) { logger.debug(`Got project ID from state manager: ${projectId}`); } else { // If not in state manager, try to get it from environment const envProjectId = process.env.GOOGLE_CLOUD_PROJECT; if (envProjectId) { projectId = envProjectId; logger.debug(`Got project ID from environment: ${projectId}`); // Store in state manager for future use await stateManager.setCurrentProjectId(projectId); } else { // If not in environment, try to get it from our function projectId = await getProjectId(); logger.debug(`Got project ID from getProjectId: ${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, }); logger.debug( `Using Spanner client with explicit project ID: ${projectId} for list-spanner-instances`, ); const [instances] = await spanner.getInstances(); if (!instances || instances.length === 0) { return { content: [ { type: "text", text: `# Spanner Instances\n\nProject: ${projectId}\n\nNo instances found in the project.`, }, ], }; } let markdown = `# Spanner Instances\n\nProject: ${projectId}\n\n`; // Table header markdown += "| Instance ID | State | Config | Nodes |\n"; markdown += "|-------------|-------|--------|-------|\n"; // Table rows for (const instance of instances) { const metadata = instance.metadata || {}; markdown += `| ${instance.id || "unknown"} | ${metadata.state || "unknown"} | ${metadata.config?.split("/").pop() || "unknown"} | ${metadata.nodeCount || "unknown"} |\n`; } // Add resource links for further exploration markdown += "\n## Available Resources\n\n"; markdown += `- All Instances: \`gcp-spanner://${projectId}/instances\`\n`; for (const instance of instances) { markdown += `- Databases in ${instance.id}: \`gcp-spanner://${projectId}/${instance.id}/databases\`\n`; } return { content: [ { type: "text", text: markdown, }, ], }; } catch (error: any) { logger.error( `Error listing Spanner instances: ${error instanceof Error ? error.message : String(error)}`, ); throw error; } }, );
• src/index.ts:167-176 (registration)

  Top-level registration of Spanner tools by calling registerSpannerTools(server), which includes the 'gcp-spanner-list-instances' tool.
  try { logger.info("Registering Google Cloud Spanner services"); registerSpannerResources(server); registerSpannerTools(server); registerSpannerQueryCountTool(server); } catch (error) { logger.warn( `Error registering Spanner services: ${error instanceof Error ? error.message : String(error)}`, ); }