Design API authentication mechanisms with consistent patterns, clear documentation, and helpful error messages. When implementing authentication:

  1. Document authentication requirements explicitly:
  2. Design credentials lookup intelligently:
    # Prefer using the base index URL for credential lookup
    # Instead of:
    credentials = keyring.get_credential(package_url, None)
       
    # Use:
    credentials = keyring.get_credential(index_url, None)
    
  3. Provide clear error messages for authentication failures:
    If you use `--token "$JFROG_TOKEN"` with JFrog, you will receive a 
    401 Unauthorized error as JFrog requires an empty username but 
    uv passes `__token__` as the username when `--token` is used.
    
  4. Consider consistency across similar operations:
  5. Test authentication edge cases: