The MongoDB MCP server — maintained by MongoDB itself — lets an AI client inspect collections, run queries and explore your schema, against a local instance or an Atlas cluster. Here is the safe setup for Claude Desktop and Cursor.
Configure the client
Pass the connection string via an environment variable (never as a CLI arg, where it can leak into process lists) and start in read-only mode:
{
"mcpServers": {
"mongodb": {
"command": "npx",
"args": ["-y", "mongodb-mcp-server@latest", "--readOnly"],
"env": {
"MDB_MCP_CONNECTION_STRING": "mongodb://localhost:27017/myDatabase"
}
}
}
}
For Atlas, use the full mongodb+srv://user:pass@cluster.mongodb.net/db string with a valid database user. Restart the client; see MCP config file location if you cannot find the file.
Why --readOnly
The flag restricts the server to non-destructive operations — the AI can query and analyse but cannot insert, update or drop. Keep it on unless you explicitly need writes, and never run write-enabled against production. This is the least-privilege principle from our MCP security best practices.
Verify
Ask: "List the collections in my database and show a sample document from users." Real data back means you are connected.
Common problems
Authentication failed— wrong user/password in the connection string, or the user lacks access to that database.connection timed out— for Atlas, your IP is not in the network access allowlist; add it in the Atlas dashboard.- Write attempts rejected — that is
--readOnly; remove it only when needed. - No tools in client — Node 18+ required; see Cursor MCP not working.
Going further
MongoDB fits a backend stack with GitHub and filesystem servers — see the best MCP stack for a backend developer and the databases category. Comparing engines? Read best MCP server for a database.