Use XOR with Claude Code

Add it

Run this in a terminal:

claude mcp add --transport http --scope user xor https://systemofreason.com/mcp

Then, in Claude Code, type /mcp, pick xor, and sign in in your browser with your email and the code we send you. You can also run claude mcp login xor.

--scope user makes XOR available in every project. Leave it out to add it to the current project only.

Already on claude.ai?

If you added XOR on claude.ai and Claude Code is signed in to the same Claude account, it’s already there. Type /mcp to check.

With an access key instead

For machines with no browser, such as a server or CI, use an access key. Keep it in XOR_KEY, and add XOR to your project’s .mcp.json:

{
  "mcpServers": {
    "xor": {
      "type": "http",
      "url": "https://systemofreason.com/mcp",
      "headers": { "Authorization": "Bearer ${XOR_KEY}" }
    }
  }
}

Claude Code fills in ${XOR_KEY} from the environment, so the key never sits in the file.

Code that uses XOR

Claude Code can also write programs that use XOR through the web API. Ask it to make a key for the program, and add the lines from for AI agents to your CLAUDE.md.