MongoDB MCP Server

Instructions

Implementation Reference

• src/tools/mongodb/metadata/listDatabases.ts:29-47 (handler)

  The `execute` method implements the core logic of the 'list-databases' tool, connecting to MongoDB, fetching databases with sizes, and returning formatted text and structured content.

  protected async execute(): Promise<CallToolResult> {
      const provider = await this.ensureConnected();
      const dbs = (await provider.listDatabases("")).databases as { name: string; sizeOnDisk: bson.Long }[];
      const databases = dbs.map((db) => ({
          name: db.name,
          size: Number(db.sizeOnDisk),
      }));
  
      return {
          content: formatUntrustedData(
              `Found ${dbs.length} databases`,
              ...dbs.map((db) => `Name: ${db.name}, Size: ${db.sizeOnDisk.toString()} bytes`)
          ),
          structuredContent: {
              databases,
              totalCount: databases.length,
          },
      };
  }

• src/tools/mongodb/metadata/listDatabases.ts:8-16 (schema)

  Zod schema defining the structured output for the list-databases tool, including an array of database names and sizes, and total count.

  export const ListDatabasesOutputSchema = {
      databases: z.array(
          z.object({
              name: z.string(),
              size: z.number(),
          })
      ),
      totalCount: z.number(),
  };

• src/tools/mongodb/tools.ts:4-4 (registration)

  Exports the ListDatabasesTool class, making it available for inclusion in the AllTools array used by the server for tool registration.

  export { ListDatabasesTool } from "./metadata/listDatabases.js";

• src/tools/mongodb/metadata/listDatabases.ts:22-48 (handler)

  The full ListDatabasesTool class definition, including name, description, schemas, and execute handler for the 'list-databases' tool.

  export class ListDatabasesTool extends MongoDBToolBase {
      public name = "list-databases";
      protected description = "List all databases for a MongoDB connection";
      protected argsShape = {};
      protected override outputSchema = ListDatabasesOutputSchema;
      static operationType: OperationType = "metadata";
  
      protected async execute(): Promise<CallToolResult> {
          const provider = await this.ensureConnected();
          const dbs = (await provider.listDatabases("")).databases as { name: string; sizeOnDisk: bson.Long }[];
          const databases = dbs.map((db) => ({
              name: db.name,
              size: Number(db.sizeOnDisk),
          }));
  
          return {
              content: formatUntrustedData(
                  `Found ${dbs.length} databases`,
                  ...dbs.map((db) => `Name: ${db.name}, Size: ${db.sizeOnDisk.toString()} bytes`)
              ),
              structuredContent: {
                  databases,
                  totalCount: databases.length,
              },
          };
      }
  }

• src/tools/index.ts:7-11 (registration)

  AllTools array construction that includes MongoDbTools (which exports ListDatabasesTool), used by server.ts for registering all tools including 'list-databases'.

  export const AllTools: ToolClass[] = Object.values({
      ...MongoDbTools,
      ...AtlasTools,
      ...AtlasLocalTools,
  });