Install Substack MCP Server in Codex

What you need first

• Codex, installed.
• Node.js, which gives the npx command the server starts with.
• Your own values for YOUR_SUBSTACK_PUBLICATION_URL,YOUR_SUBSTACK_SESSION_TOKEN,YOUR_SUBSTACK_USER_ID.

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 substack-mcp --env SUBSTACK_PUBLICATION_URL=YOUR_SUBSTACK_PUBLICATION_URL --env SUBSTACK_SESSION_TOKEN=YOUR_SUBSTACK_SESSION_TOKEN --env SUBSTACK_USER_ID=YOUR_SUBSTACK_USER_ID -- npx -y [email protected]

2. Replace YOUR_SUBSTACK_PUBLICATION_URL,YOUR_SUBSTACK_SESSION_TOKEN,YOUR_SUBSTACK_USER_ID with your own values.
3. Start Codex again and type /mcp: the server is listed.

Check it worked

Ask Codex: List the tools of substack-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.