gcp-spanner-list-tables

Lists all tables in a Google Cloud Spanner database to view database structure and schema information. Specify instance and database IDs to retrieve table names.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`instanceId`	No	Spanner instance ID (defaults to SPANNER_INSTANCE env var)
`databaseId`	No	Spanner database ID (defaults to SPANNER_DATABASE env var)

Implementation Reference

src/services/spanner/tools.ts:164-241 (handler)

The handler function executes the tool logic: retrieves project and Spanner config, runs SQL query on information_schema.tables to list tables and column counts, formats results as Markdown table with project/instance/database info and resource URIs.

async ({ instanceId, databaseId }, _extra) => {
  try {
    const projectId = await getProjectId();
    const config = await getSpannerConfig(
      Array.isArray(instanceId) ? instanceId[0] : instanceId,
      Array.isArray(databaseId) ? databaseId[0] : databaseId,
    );

    const spanner = await getSpannerClient();
    logger.debug(
      `Using Spanner client with project ID: ${spanner.projectId} for execute-spanner-query`,
    );
    const instance = spanner.instance(config.instanceId);
    const database = instance.database(config.databaseId);

    // Query for tables
    // Execute query to list tables
    const [tablesResult] = await database.run({
      sql: `SELECT t.table_name, 
                (SELECT COUNT(1) FROM information_schema.columns 
                 WHERE table_name = t.table_name) as column_count
          FROM information_schema.tables t
          WHERE t.table_catalog = '' AND t.table_schema = ''
          ORDER BY t.table_name`,
    });

    if (!tablesResult || tablesResult.length === 0) {
      return {
        content: [
          {
            type: "text",
            text: `# Spanner Tables\n\nProject: ${projectId}\nInstance: ${config.instanceId}\nDatabase: ${config.databaseId}\n\nNo tables found in the database.`,
          },
        ],
      };
    }

    let markdown = `# Spanner Tables\n\nProject: ${projectId}\nInstance: ${config.instanceId}\nDatabase: ${config.databaseId}\n\n`;

    // Table header
    markdown += "| Table Name | Column Count |\n";
    markdown += "|------------|-------------|\n";

    // Table rows
    for (const row of tablesResult) {
      // Access the row properties directly

      // Extract table name and column count
      const tableName = ((row as any).table_name as string) || "unknown";
      const columnCount = ((row as any).column_count as number) || 0;

      markdown += `| ${tableName} | ${columnCount} |\n`;
    }

    // Add resource links for further exploration
    markdown += "\n## Available Resources\n\n";
    markdown += `- Schema: \`gcp-spanner://${projectId}/${config.instanceId}/${config.databaseId}/schema\`\n`;

    for (const row of tablesResult) {
      const tableName = ((row as any).table_name as string) || "unknown";
      markdown += `- Table Preview: \`gcp-spanner://${projectId}/${config.instanceId}/${config.databaseId}/tables/${tableName}/preview\`\n`;
    }

    return {
      content: [
        {
          type: "text",
          text: markdown,
        },
      ],
    };
  } catch (error: any) {
    logger.error(
      `Error listing Spanner tables: ${error instanceof Error ? error.message : String(error)}`,
    );
    throw error;
  }
},

src/services/spanner/tools.ts:155-163 (schema)

Input schema using Zod for optional instanceId and databaseId parameters, with descriptions.

  instanceId: z
    .string()
    .optional()
    .describe("Spanner instance ID (defaults to SPANNER_INSTANCE env var)"),
  databaseId: z
    .string()
    .optional()
    .describe("Spanner database ID (defaults to SPANNER_DATABASE env var)"),
},

src/services/spanner/tools.ts:152-242 (registration)

Registration of the 'gcp-spanner-list-tables' tool using server.tool() inside the registerSpannerTools function.

server.tool(
  "gcp-spanner-list-tables",
  {
    instanceId: z
      .string()
      .optional()
      .describe("Spanner instance ID (defaults to SPANNER_INSTANCE env var)"),
    databaseId: z
      .string()
      .optional()
      .describe("Spanner database ID (defaults to SPANNER_DATABASE env var)"),
  },
  async ({ instanceId, databaseId }, _extra) => {
    try {
      const projectId = await getProjectId();
      const config = await getSpannerConfig(
        Array.isArray(instanceId) ? instanceId[0] : instanceId,
        Array.isArray(databaseId) ? databaseId[0] : databaseId,
      );

      const spanner = await getSpannerClient();
      logger.debug(
        `Using Spanner client with project ID: ${spanner.projectId} for execute-spanner-query`,
      );
      const instance = spanner.instance(config.instanceId);
      const database = instance.database(config.databaseId);

      // Query for tables
      // Execute query to list tables
      const [tablesResult] = await database.run({
        sql: `SELECT t.table_name, 
                  (SELECT COUNT(1) FROM information_schema.columns 
                   WHERE table_name = t.table_name) as column_count
            FROM information_schema.tables t
            WHERE t.table_catalog = '' AND t.table_schema = ''
            ORDER BY t.table_name`,
      });

      if (!tablesResult || tablesResult.length === 0) {
        return {
          content: [
            {
              type: "text",
              text: `# Spanner Tables\n\nProject: ${projectId}\nInstance: ${config.instanceId}\nDatabase: ${config.databaseId}\n\nNo tables found in the database.`,
            },
          ],
        };
      }

      let markdown = `# Spanner Tables\n\nProject: ${projectId}\nInstance: ${config.instanceId}\nDatabase: ${config.databaseId}\n\n`;

      // Table header
      markdown += "| Table Name | Column Count |\n";
      markdown += "|------------|-------------|\n";

      // Table rows
      for (const row of tablesResult) {
        // Access the row properties directly

        // Extract table name and column count
        const tableName = ((row as any).table_name as string) || "unknown";
        const columnCount = ((row as any).column_count as number) || 0;

        markdown += `| ${tableName} | ${columnCount} |\n`;
      }

      // Add resource links for further exploration
      markdown += "\n## Available Resources\n\n";
      markdown += `- Schema: \`gcp-spanner://${projectId}/${config.instanceId}/${config.databaseId}/schema\`\n`;

      for (const row of tablesResult) {
        const tableName = ((row as any).table_name as string) || "unknown";
        markdown += `- Table Preview: \`gcp-spanner://${projectId}/${config.instanceId}/${config.databaseId}/tables/${tableName}/preview\`\n`;
      }

      return {
        content: [
          {
            type: "text",
            text: markdown,
          },
        ],
      };
    } catch (error: any) {
      logger.error(
        `Error listing Spanner tables: ${error instanceof Error ? error.message : String(error)}`,
      );
      throw error;
    }
  },
);

src/index.ts:169-170 (registration)
Call to registerSpannerTools(server) in the main server initialization, which registers the Spanner tools including gcp-spanner-list-tables.
```
registerSpannerResources(server);
registerSpannerTools(server);
```
src/services/spanner/index.ts:13-13 (registration)
Re-export of registerSpannerTools from tools.ts for use in main index.ts.
```
export { registerSpannerTools } from "./tools.js";
```

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