Google Cloud MCP Server

Implementation Reference

• src/services/spanner/tools.ts:349-429 (handler)

  The main execution handler for the 'gcp-spanner-list-databases' tool. Retrieves project ID from state or auth, creates Spanner client, lists databases for the given instanceId, formats results as Markdown table with project/instance info and resource URIs for tables/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;
          logger.debug(`Got project ID from getProjectId: ${projectId}`);
        }
      } else {
        logger.debug(`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,
      });
  
      logger.debug(
        `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) {
      logger.error(
        `Error listing Spanner databases: ${error instanceof Error ? error.message : String(error)}`,
      );
      throw error;
    }

• src/services/spanner/tools.ts:346-348 (schema)

  Zod input schema for the tool, requiring 'instanceId' as a string.

  {
    instanceId: z.string().describe("Spanner instance ID"),
  },

• src/services/spanner/tools.ts:344-431 (registration)

  Direct registration of the tool via server.tool() call inside registerSpannerTools(), specifying name, schema, and inline handler.

  server.tool(
    "gcp-spanner-list-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;
            logger.debug(`Got project ID from getProjectId: ${projectId}`);
          }
        } else {
          logger.debug(`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,
        });
  
        logger.debug(
          `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) {
        logger.error(
          `Error listing Spanner databases: ${error instanceof Error ? error.message : String(error)}`,
        );
        throw error;
      }
    },
  );

• src/index.ts:170-170 (registration)

  Top-level call to registerSpannerTools(server) in the main server initialization, which triggers the tool registrations including gcp-spanner-list-databases.

  registerSpannerTools(server);