fx

Connect fx to the Kernel MCP server

Install with the Kernel CLI

Run the following command:

kernel mcp install --target fx

Configure manually

Alternatively, add Kernel to the mcp map in ~/.fx/mcp.json:

{
  "mcp": {
    "kernel": {
      "type": "http",
      "url": "https://mcp.onkernel.com/mcp",
      "oauth": {}
    }
  }
}

Connect

Start fx, or reload the configuration in an existing session:

/mcp reload

Then authenticate with Kernel:

/mcp auth kernel --open

Authorize access in the browser window that opens. You can then run /mcp list to verify that Kernel is connected.

Headless and scripted use

/mcp auth needs a browser, so it only works in an interactive fx session. Non-interactive runs — fx ask, fx acp, CI — can’t complete it: fx returns Run /mcp auth for this server in an interactive fx session and the Kernel tools aren’t discoverable.

For these, authenticate with a Kernel API key instead of OAuth. Get one from the Kernel Dashboard, export it, and reference it from ~/.fx/mcp.json with bearer_token_env:

export KERNEL_API_KEY="sk_..."

{
  "mcp": {
    "kernel": {
      "type": "http",
      "url": "https://mcp.onkernel.com/mcp",
      "bearer_token_env": "KERNEL_API_KEY"
    }
  }
}

fx rejects a literal Authorization header in a static headers field (the format other MCP clients use for API-key auth) to keep credentials out of the profile file. bearer_token_env is the fx-specific equivalent — it points at an environment variable instead of embedding the token.

Running kernel mcp install --target fx always writes the OAuth config above, so switch to bearer_token_env by hand for headless use.