MCP MongoDB Server

A Model Context Protocol (MCP) server that lets AI assistants work with your MongoDB databases. It exposes your collections, infers their schemas, and runs queries, aggregations, and writes through a standard interface — so tools like Claude Desktop and Cursor can read and reason about your data.

Demo

Why use it

• Talk to your database in plain language — the assistant discovers your collections and their shape automatically.
• Safe by default — turn on read-only mode to let an assistant explore without any risk of changing data.
• Works everywhere — connects to standalone, replica set, sharded, and Atlas deployments, over plain or TLS connections.

Key Features

• Read-Only Mode — blocks every write path (insert, update, index creation, and aggregation stages like `$out`/`$merge` that could modify data).
• Smart ObjectId Handling — configurable `auto`/`none`/`force` conversion of 24-character hex strings to ObjectIds.
• Schema Inference — automatic collection schema detection from document samples.
• Query & Aggregation — full query and aggregation pipeline support, with optional `explain` plans.
• Write Operations — insert, update, and index creation (when read-only mode is off).
• Time Conversion — a `convertTime` helper turns Unix timestamps and date strings into UTC/GMT/ISO, so date queries stay unambiguous across timezones.
• Progress & Cancellation — long operations report progress and can be cancelled mid-flight.
• Two Transports — run locally over stdio, or expose an HTTP endpoint for remote access.

Requirements

• Node.js 20 or newer

Quick Start

Point the server at your database — no install step needed:

npx -y mcp-mongo-server mongodb://localhost:27017/mydatabase

Explore safely, without any chance of changing data:

npx -y mcp-mongo-server mongodb://localhost:27017/mydatabase --read-only

Usage

Local (stdio)

This is the default, used by Claude Desktop, Cursor, and other local clients:

npx -y mcp-mongo-server "mongodb://user:pass@localhost:27017/mydatabase"

Remote (HTTP)

Expose an HTTP endpoint at `/mcp` for remote or multi-client access:

npx -y mcp-mongo-server "mongodb://user:pass@localhost:27017/mydatabase" --transport http --port 3001

By default, only requests without a browser `Origin` (CLIs, IDEs) and requests

from `localhost` are accepted; everything else is rejected with `403` to guard

against DNS-rebinding attacks. Allow specific browser origins with

`--allowed-origins`:

npx -y mcp-mongo-server "mongodb://..." --transport http --port 3001 --allowed-origins "https://app.example.com"

Options

Environment Variables

Security

Database scope. The server operates on the database in your connection

string. Aggregation stages that reach another database (`$out`, `$merge`,

`$lookup` with an explicit `db`) are rejected by default, so a pipeline can't

quietly read from or write to databases you didn't point it at. Enable them

with `--allow-cross-db` if you need them.

Server-side JavaScript. The aggregation operators `$function`, `$where`,

and `$accumulator` run arbitrary JavaScript on the MongoDB server. They are

rejected by default; enable them with `--allow-server-js` if you trust the

pipelines being run.

Read-only mode blocks every write path, including aggregation stages that

write or run server-side JavaScript (`$out`, `$merge`, `$function`, `$where`,

`$accumulator`).

Least privilege. Application-level checks only go so far — the strongest

guarantee comes from the database. Connect with a MongoDB user scoped to just

the database you need, with read-only permissions when the assistant only needs

to explore. That way the database itself enforces the boundary, as defense in

depth.

Documentation

• Integration Guide — Claude Desktop, Windsurf, Cursor, Docker
• Available Tools — query, aggregate, update, insert, and more
• Development — setup, scripts, and debugging
• Contributing

License

MIT — see LICENSE for details.