I agree, there's rough edges everywhere. But you can rephrase the question as "how does a cron expression work", and do the interpretation yourself. It returns perfectly sensible results that would enable a perfectly sensible person to quickly write and interpret a cron expression.

This is what I meant when I implied it won't replace you as a thinking agent, but it sure can bring information to you quickly. `man cron` works fine, too, but sometimes it's nice to have one interface, and be able to ask clarifying questions.