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Spec{0}

Connect Cursor

Add Spec0 (global)

Open or create ~/.cursor/mcp.json and add:

{
  "mcpServers": {
    "spec0": {
      "url": "http://127.0.0.1:7474/mcp"
    }
  }
}

Restart Cursor (fully — quit and reopen, not just close the window). Cursor will pick up Spec0 on next launch.

Or per project

Put the same JSON in .cursor/mcp.json at the root of the project you want Cursor to connect from. Project-level config wins over the global one for that project.

Optional fields

headers for static auth and auth for OAuth are both supported. Neither applies to Spec0, since it accepts local-loopback connections without auth. You can also interpolate environment variables in url and headers with ${env:VAR_NAME}.

Verify the connection

In the Cursor chat, ask:

Call the spec0_whoami tool.

The agent should return a JSON object with kind: "cursor" (or similar) and a fresh session.id. If whoami works, the rest of the Spec0 tools are available too.

Tips

  • Cursor only re-reads mcp.json on a full restart. A reload of the window is not enough.
  • If the server doesn’t show in the Cursor tools panel, check that Spec0 is actually running and listening — open it from /Applications/Spec0.app and confirm the MCP indicator in the bottom of the sidebar shows green.