How to turn a Python API client into a CLI tool without writing a parser

Developers who build Python classes to wrap HTTP APIs often need a command-line interface to run quick checks or schedule cron jobs, which traditionally requires writing a verbose argparse layer. This approach is error-prone because any new parameter added to the client can easily be missed in the CLI code. The open-source library jsonargparse offers an alternative by automatically deriving a CLI from a class's type hints and docstrings using a single function call, auto_cli. A practical walkthrough demonstrates this using the USGS Earthquake Catalog API, a free, no-key-required service that logs seismic events worldwide in real time. The technique requires Python 3.10 or later and works with existing client classes as long as their type hints and docstrings are complete.