count_documents
Count documents in a MongoDB collection that match specific criteria to understand data volume and optimize queries without retrieving full documents.
Instructions
Count documents in a collection that match a filter.
Benefits:
More efficient than retrieving full documents
Good for understanding data volume
Can help planning query strategies
Optimize pagination implementation
Example: use_mcp_tool with server_name: "mongodb", tool_name: "count_documents", arguments: { "collection": "users", "filter": { "active": true, "age": { "$gte": 21 } } }
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| database | No | Database name (optional if default database is configured) | |
| collection | Yes | Collection name | |
| filter | No | MongoDB query filter (optional, defaults to count all documents) |
Implementation Reference
- src/index.ts:1359-1384 (handler)Handler for the count_documents tool. Extracts parameters, connects to the MongoDB database, executes countDocuments(filter) on the specified collection, and returns the count in JSON format.
case 'count_documents': { const { database, collection, filter = {} } = request.params.arguments as { database?: string; collection: string; filter?: object; }; const dbName = database || this.defaultDatabase; if (!dbName) { throw new McpError( ErrorCode.InvalidRequest, 'Database name is required when no default database is configured' ); } const db = client.db(dbName); const count = await db.collection(collection).countDocuments(filter); return { content: [ { type: 'text', text: JSON.stringify({ count }, null, 2), }, ], }; } - src/index.ts:757-792 (registration)Tool registration entry for count_documents, defining its name, description, and input schema for the ListToolsRequestSchema handler.
name: 'count_documents', description: `Count documents in a collection that match a filter. Benefits: - More efficient than retrieving full documents - Good for understanding data volume - Can help planning query strategies - Optimize pagination implementation Example: use_mcp_tool with server_name: "mongodb", tool_name: "count_documents", arguments: { "collection": "users", "filter": { "active": true, "age": { "$gte": 21 } } }`, inputSchema: { type: 'object', properties: { database: { type: 'string', description: 'Database name (optional if default database is configured)', }, collection: { type: 'string', description: 'Collection name', }, filter: { type: 'object', description: 'MongoDB query filter (optional, defaults to count all documents)', }, }, required: ['collection'], }, }, - src/index.ts:774-791 (schema)Input schema definition for the count_documents tool, specifying parameters: database (optional), collection (required), and filter (optional).
inputSchema: { type: 'object', properties: { database: { type: 'string', description: 'Database name (optional if default database is configured)', }, collection: { type: 'string', description: 'Collection name', }, filter: { type: 'object', description: 'MongoDB query filter (optional, defaults to count all documents)', }, }, required: ['collection'], },