MCP Server Boilerplate

Instructions

Implementation Reference

• src/index.ts:140-166 (handler)

  Handler function that ensures MongoDB connection, queries the collection with optional filter and limit, fetches documents, formats output, and returns formatted results as text content.
  async ({ database: dbName, collection: collectionName, filter = {}, limit }) => { try { const db = await ensureConnection(dbName); const collection: Collection = db.collection(collectionName); let cursor = collection.find(filter); if (limit) { cursor = cursor.limit(limit); } const documents = await cursor.toArray(); const formattedOutput = formatJsonOutput(documents); return { content: [ { type: "text", text: `Found ${documents.length} document(s):\n\n${formattedOutput}`, }, ], }; } catch (error) { throw new Error(`Failed to find documents: ${error instanceof Error ? error.message : 'Unknown error'}`); } } );
• src/index.ts:134-139 (schema)

  Zod input schema defining parameters for the tool: database name, collection name, optional query filter, and optional limit.
  { database: z.string().describe("Database name"), collection: z.string().describe("Collection name"), filter: z.record(z.any()).optional().describe("Query filter as JSON object (optional)"), limit: z.number().optional().describe("Maximum number of documents to return (optional)"), },
• src/index.ts:131-133 (registration)

  Registration of the mongo-find-documents tool using server.tool() with name and description.
  server.tool( "mongo-find-documents", "Query documents from a MongoDB collection",
• src/index.ts:64-78 (helper)

  Helper function to format JSON output, truncating large data and cleaning up placeholder strings for better readability.
  function formatJsonOutput(data: unknown): string { const truncatedData = truncateForOutput(data); let outputText = JSON.stringify(truncatedData, null, 2); outputText = outputText.replace( /"\.\.\.(\d+) more items"/g, "...$1 more items" ); outputText = outputText.replace( /"\.\.\.(\d+) more properties": "\.\.\.?"/g, "...$1 more properties" ); return outputText; }
• src/index.ts:88-100 (helper)

  Helper function to establish and reuse MongoDB connection and database instances.
  async function ensureConnection(dbName: string): Promise<Db> { if (!mongoClient) { const uri = getMongoUri(); mongoClient = new MongoClient(uri); await mongoClient.connect(); } if (!databases.has(dbName)) { databases.set(dbName, mongoClient.db(dbName)); } return databases.get(dbName)!; }