In regards to the ssh-agent stuff (and a lot of the other CLI tricks), the man pages usually document them. They may lag a bit for new features, but most of them will have a man page. Barring that they’ll usually print a help message.

One command off the top of my head that doesn’t really follow this is the undocumented/internal `airport` command. In that case it has two different help messages depending on how it’s called, and is also tucked away in a framework as well.