mongo-find-documents

Query documents from a MongoDB collection using database name, collection name, and optional filters to retrieve specific data records.

Instructions

Query documents from a MongoDB collection

Input Schema

TableJSON Schema

Name	Required	Description
`database`	Yes	Database name
`collection`	Yes	Collection name
`filter`	No	Query filter as JSON object (optional)
`limit`	No	Maximum number of documents to return (optional)

Implementation Reference

src/index.ts:140-165 (handler)

The handler function that executes the mongo-find-documents tool: connects to MongoDB database, finds documents using the provided filter and optional limit, formats the output as truncated JSON, and returns it in the MCP response format.

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 schema for the tool's input parameters: required database and collection names, optional filter object and limit number.

{
  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:131-166 (registration)

Registration of the "mongo-find-documents" tool with the MCP server, specifying name, description, input schema, and inline handler function.

server.tool(
  "mongo-find-documents",
  "Query documents from a MongoDB collection",
  {
    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)"),
  },
  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:88-100 (helper)

Helper function to ensure a MongoDB connection and database instance is available, used by the tool handler.

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)!;
}

src/index.ts:64-78 (helper)

Helper function to format and clean up truncated JSON output for the tool response, called by the handler.

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;
}

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