Declarative hyperparameter management for ML/AI experiments. Use when Claude needs to:
(1) Create CLI applications with type-hinted parameters and auto-generated help
(2) Configure ML training scripts with @proto.cli, @proto.prefix, or @proto decorators
(3) Set up multi-namespace configurations with namespaced CLI arguments
(4) Read configuration from environment variables using EnvVar
(5) Create hyperparameter sweeps using piter or Sweep
(6) Work with Union types for subcommand-like CLI patterns