Install MERN MCP in Codex

What you need first

• Codex, installed.
• Node.js, which gives the npx command the server starts with.
• Your own value for YOUR_MERN_MCP_PROJECT_ROOT.

Steps

1. Run this in a terminal. It writes the server into ~/.codex/config.toml, which the Codex CLI, its IDE extension and the ChatGPT desktop app share.

codex mcp add mern-mcp --env MERN_MCP_PROJECT_ROOT=YOUR_MERN_MCP_PROJECT_ROOT -- npx -y [email protected]

2. Replace YOUR_MERN_MCP_PROJECT_ROOT with your own value.
3. Start Codex again and type /mcp: the server is listed.

Check it worked

Ask Codex: List the tools of mern-mcp.

If it does not start

spawn npx ENOENT

Node.js is not on the PATH that Codex sees. Install it, or write the full path of npx in the config.

The server starts, but its tools fail

A YOUR_… placeholder is still in the config, or its value is wrong.