Install groundtruth-mcp in Codex

What you need first

• Codex, installed.
• Node.js, which gives the npx command the server starts with.

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 ethglobal-cannes-2026-groundtruth -- npx -y groundtruth-mcp

2. Start Codex again and type /mcp: the server is listed.

Check it worked

Ask Codex: List the tools of ethglobal-cannes-2026-groundtruth.

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.