MongoDB MCP Server

Instructions

Implementation Reference

• src/index.ts:1024-1043 (handler)

  The handler function for the 'list_collections' tool. It extracts the optional database name from arguments, connects to the specified or default database, lists all collections using db.listCollections().toArray(), and returns the result as JSON-formatted text content.

  case 'list_collections': {
    const { database } = request.params.arguments as { database?: string };
    const dbName = database || this.defaultDatabase;
    if (!dbName) {
      throw new McpError(
        ErrorCode.InvalidRequest,
        'Database name is required when no default database is configured'
      );
    }
    const db = client.db(dbName);
    const collections = await db.listCollections().toArray();
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(collections, null, 2),
        },
      ],
    };
  }

• src/index.ts:325-333 (schema)

  Input schema definition for the 'list_collections' tool, specifying an optional 'database' string parameter.

  inputSchema: {
    type: 'object',
    properties: {
      database: {
        type: 'string',
        description: 'Database name (optional if default database is configured)',
      },
    },
  },

• src/index.ts:320-334 (registration)

  Registration of the 'list_collections' tool in the list of tools provided by the ListToolsRequestSchema handler, including name, description, and input schema.

          {
            name: 'list_collections',
            description: `List all collections in a database.
            
  Start here to understand what collections are available before querying.`,
            inputSchema: {
              type: 'object',
              properties: {
                database: {
                  type: 'string',
                  description: 'Database name (optional if default database is configured)',
                },
              },
            },
          },