This library is used by Prawn to generate its self-documenting manual, and could be used by third-party Prawn extensions to create manuals for their functionality as well.
It is in a very early stage of maintenance, and is not yet officially supported for use outside of Prawn. However, you're welcome to use it at your own risk!
Prawn::ManualBuilder was initially developed as an internal tool for Prawn by Felipe Doria, and is now maintained by Gregory Brown.