Are there any similar, open-source libraries for database schema introspection and documentation? For example, I would like to provide a UI for users to documen

Are there any similar, open-source libraries for database schema introspection and documentation? For example, I would like to provide a UI for users to document database tables and columns. At a higher level, it would also be useful to audit views to get an idea of which tables and columns are in high demand and might need indexes.