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Securing an API Key for the TfL API

An API key is strongly recommended for effective use. Without one, TfL strictly rate-limits anonymous requests to a handful per minute per IP address, which will impact most real-world usage.

Providing the TFL_APP_KEY environment variable significantly raises the rate limits, allowing continuous AI usage. Optionally, you can also provide TFL_APP_ID alongside TFL_APP_KEY if your TfL registration issued you an App ID (older registrations).

Steps to Register an API Key

  1. Go to the TfL API Portal Registration Page.
  2. Create an account and verify your email.
  3. Once logged in, navigate strictly to the Products section and register for the "500 requests per min" default tier product.
  4. Retrieve the Primary Key generated for your application.

Passing the Key to the MCP Server

For a source-based stdio configuration, pass it via the env dictionary in your claude_desktop_config.json. The MCPB installer exposes the same value as a sensitive configuration field.

"env": {
  "TFL_APP_KEY": "your_primary_key"
}

For Docker, expose the client process environment and ask Docker to forward it into the container:

"args": [
  "run",
  "-i",
  "--rm",
  "-e",
  "TFL_APP_KEY",
  "ghcr.io/oneill9/tfl-mcp-server:latest"
],
"env": {
  "TFL_APP_KEY": "your_primary_key"
}