Want to write a Form Tools module? Awesome! There's an awful lot of information in this section, but we do recommend slogging your way through the whole thing. Even if you don't catch all the details it will still give you a sense of how it works and what exists to make your life easier. It won't be time wasted, honest.
Form Tools 2 and 3 have a completely different codebase, so start by picking your Form Tools version.