The pyproject.toml file is described in [PEP 621](https://peps.python.org/pep-0621/). It is the recommended way to package Python projects these days. On the other hand, setup.py is obsolete, but not yet [deprecated](https://packaging.python.org/en/latest/discussions/setup-py-deprecated/). More on the migration in https://packaging.python.org/en/latest/guides/modernize-setup-py-project/ If I have spare time, I will open a PR.