The Mautic API documentation seems to be out of date, from the Mautic 2 era. It refers to a PHP API library that has to be installed, but the provided links - like this one - are dead.
This link works, but the documentation does not provide any details which files from Github should be installed where in your project - install via Composer is the only option?
Is the API documentation still valid for version 4? I have not been able to make the API work with the provided documentation.