MongoDB MCP in Claude Code

Quick answer: Install the MongoDB MCP server with npx -y mongodb-mcp-server, add the JSON block below to ~/.claude/settings.json, restart Claude Code, and run /mcp to confirm the connection. Setup runs about 5 minutes on a fresh machine, verified on mongodb-mcp-server as of April 15, 2026.

The MongoDB MCP server hands Claude Code a query and admin surface on top of a MongoDB deployment. After setup, the model can list databases, run finds and aggregations, inspect indexes, and insert or update documents. The server is published as mongodb-mcp-server and uses a standard connection URI for auth.

This guide covers what you get after the wiring is done, the exact config, verification steps, prompt patterns that tend to work well, and the 4 issues that trip people up most often in the first week.

What you get when it is connected

Once the MongoDB server is attached, Claude Code can call the server tools from inside any conversation. You do not invoke the tools by hand. When you ask Claude a question the model decides which tool to call and parses the response for you. For teams that live inside MongoDB day to day, this replaces dozens of context switches per week with a single line in chat.

Tools exposed include list_databases, list_collections, find, aggregate, insert_one, insert_many, update_one, delete_one, count, create_index, drop_index. Change streams and transactions are not exposed through the MCP surface, so for those workflows use the Node driver directly. BSON-specific types like ObjectId serialize as strings in tool responses.

Prerequisites

A MongoDB 5+ deployment, either self-hosted or Atlas. A connection URI including username and password. Node 20 or later on the host running Claude Code.

If you use a version manager like nvm or asdf for Node, confirm the version Claude Code inherits. Open a terminal, run node -v, and note the output. Claude Code uses the Node it sees on PATH at launch, so a shell profile that sets the right version is the reliable path.

Install via npx

Run the package once with npx to verify it starts cleanly:

npx -y mongodb-mcp-server

The first run downloads the package (a few MB) and starts the server on stdio. The server does not print much on success - it waits for MCP protocol messages on stdin. Press Ctrl-C to stop it. The actual runtime setup happens through Claude Code itself in the next step.

If the install fails with a network error, your npm registry may be blocked. Set npm config set registry https://registry.npmjs.org and retry. Behind a corporate proxy, also set HTTP_PROXY and HTTPS_PROXY in your shell.

Add the config block to ~/.claude/settings.json

Open ~/.claude/settings.json in your editor. If the file does not exist yet, create it with {} as the starting content. Add an mcpServers object with an entry for this server:

{
  "mcpServers": {
    "mongodb": {
      "command": "npx",
      "args": ["-y", "mongodb-mcp-server"],
      "env": {
        "MONGODB_URI": "mongodb+srv://user:pw@cluster.mongodb.net/app"
      }
    }
  }
}

Save the file. If you already have other MCP servers defined, merge the new entry into the existing mcpServers object rather than replacing it.

Restart Claude Code fully (quit and reopen, not just close the window). The server is spawned lazily on the first tool call in a session, not at launch, but the config is read once per Claude Code start.

Verify the connection

Open a new Claude Code session and type /mcp at the prompt. You should see the server listed with a green or connected indicator. If it shows as failed, click into it for the stderr output - the error message usually points at the problem directly (bad token, wrong path, missing Node).

Run a trivial first prompt to confirm round trips work. Good smoke tests:

• For read servers: ask for a list of whatever resource type it exposes.
• For write servers: ask for a describe on a known resource first, then try a safe write on a test resource.

If the first prompt works, the wiring is done. From here on you interact with the server purely through normal prompts in Claude Code.

Example prompts that work well

Here are prompts that tend to get good responses once the server is attached:

• List every collection in the app database and tell me how many documents each one has.
• Find the 10 most recent orders in the orders collection sorted by createdAt descending.
• Run an aggregation on users that groups by country and returns the count per country.
• Show me the indexes on the events collection and tell me which fields are indexed.
• Insert a document into feedback with fields user_id, rating 5, body The onboarding was smooth.
• Find any document in users where the email field is missing and return the first 20 matches.

Claude will chain tool calls on its own when the prompt implies several steps. For a summarize-then-write flow the model will often call read tools first, then a single write tool at the end. If a prompt keeps burning tool calls, narrow it: specify the resource ID, the time range, or the exact field you want rather than asking Claude to scan everything.

Environment variable security

The connection URI lives in MONGODB_URI. It contains the password, so keep it out of committed files. Atlas supports per-user credentials you can scope to a specific database and a specific set of actions; use that to give Claude read-mostly access rather than admin access. Rotate the URI password from the Atlas dashboard if it leaks.

A general rule across every MCP server: never paste secrets directly into settings.json that lives in a shared or git-tracked directory. Keep the actual secret values in your shell profile (~/.zshrc, ~/.bashrc, or a 1Password-cli helper), export them at shell start, and reference the variable names from the Claude config. That way the secret stays on your machine and the config file is safe to share with teammates.

On macOS, terminals launched from Spotlight or from the Dock both inherit the shell profile. If you launch Claude Code from a GUI shortcut that does not go through a shell, env vars may not propagate - launch from a terminal instead.

Troubleshooting

Connection fails with authentication failed. The username or password in the URI is wrong. Check the Atlas Database Access page and confirm the user exists with the password you used. Special characters in passwords need URL encoding.

Atlas connection times out. Your IP is not in the Atlas network access allowlist. Open Network Access in the Atlas UI and add your current IP, or temporarily allow 0.0.0.0/0 for testing. Remove the broad allowlist after.

Aggregations return truncated results. The server caps tool responses around 1 MB. Add a $limit stage to the pipeline or project only the fields you actually need.

Writes refuse with role not authorized. The connection user lacks the readWrite role on the target database. Update the user in Atlas or grant the role via db.grantRolesToUser in the shell.

For any issue not listed here, the first step is /mcp inside Claude Code to see the current status and any recent stderr from the server. The second step is running the exact npx command from your terminal to see if the server starts cleanly outside Claude Code. Between those two checks, most problems become obvious within a minute.

Next steps

Once the MongoDB server is attached and verified, the useful next move is writing a short prompt template you keep in your notes. List the 3 or 4 prompts you run most often against this server, and paste them into Claude Code when needed. Over a few weeks you build a personal command library that gets real work done without typing much.

For team projects, commit a .mcp.json at the repo root with the same structure. Everyone on the team gets the server wired up automatically on first open, and individual secrets stay in shell profiles. That is the setup pattern that scales past a single developer.