if it’s online - adding docs is recursive to the base url, so you can decide if you want the entire documentation site or just one directory. for example: https://supabase.com/docs (all of supabase) or https://supabase.com/docs/reference/javascript/ (just the js docs)
if in your codebase, maybe try to split into logical subfolders so that you are not just praying that the retriever will find the right stuff when you do @codebase, then you @thisfolder or @thatfolder