The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.
You may also find the [Formula Cookbook](https://github.com/Homebrew/brew/blob/master/docs/Formula-Cookbook.md) and [Ruby Style Guide](https://github.com/styleguide/ruby) helpful in creating formulae.
