Install phoenix-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 phoenix -- npx -y phoenix-mcp

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

Check it worked

Ask Codex: List the tools of phoenix.

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.