Install mcp/ref-tools-mcp in Codex

What you need first

• Codex, installed.
• Docker, which gives the docker 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 ref-tools-mcp-rjjc4m -- docker run -i --rm docker.io/mcp/ref-tools-mcp

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

Check it worked

Ask Codex: List the tools of ref-tools-mcp-rjjc4m.

If it does not start

Cannot connect to the Docker daemon

Docker is not running. Start it, then restart Codex.