Mongo 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

MCP MongoDB Server Demo | Claude Desktop

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

Flag	Description
--read-only, -r	Block all write operations
--allow-cross-db	Allow aggregation $out/$merge/$lookup to target other databases (off by default)
--allow-server-js	Allow server-side JavaScript operators $function/$where/$accumulator (off by default)
--transport, -t	stdio (default) or http
--port, -p	HTTP port (default 3001)
--allowed-origins	Comma-separated browser origins to allow in HTTP mode
--json-limit	Max HTTP request body size (default 10mb)
--auth-token	Require Authorization: Bearer <token> on the HTTP endpoint

Environment Variables

Variable	Description
MCP_MONGODB_URI	MongoDB connection URI (alternative to the argument)
MCP_MONGODB_READONLY	Enable read-only mode ("true")
MCP_MONGODB_ALLOW_CROSS_DB	Allow cross-database aggregation stages ("true")
MCP_MONGODB_ALLOW_SERVER_JS	Allow server-side JavaScript operators ("true")
MCP_PORT	HTTP port
MCP_HTTP_ALLOWED_ORIGINS	Comma-separated browser origins to allow in HTTP mode
MCP_HTTP_JSON_LIMIT	Max HTTP request body size (default 10mb)
MCP_HTTP_AUTH_TOKEN	Bearer token required to access the HTTP endpoint

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.