ChatGPT

The ChatGPT desktop app, Codex, and the IDE extension share one MCP config. Sign in on this machine first. See Sign in. et must be on your PATH.

Desktop app

1. Open Settings, then select MCP servers.
2. Select Add server.
3. Name the server endlesstesting. Choose STDIO. Set the command to et and the argument to mcp.
4. Save, then select Restart.
5. In the composer, type /mcp and confirm endlesstesting is connected.

The same setup from a terminal:

codex mcp add endlesstesting -- et mcp

That is the config in Codex:

[mcp_servers.endlesstesting]
command = "et"
args = ["mcp"]

Tool names match the tools reference.

ChatGPT on the web uses plugins and remote tools. It does not start the local et binary. Use the desktop app for this server.