Depends on the kind of information in a directory.
For nearly every directory I describe what kind of material belongs here. Once your storage exceeds a few tens of documents, a hierarchical structure with nouns or short phrases will not describe succinctly enough what the stuff is about.
I keep a store of reference material from different sources. One directory might stand for a topic and the notes for the directory outline the provenience and the quality of the material contained therein, as well as stuff still to be provided, work to be done. Individual document might need further documentation, including but not limited to meta data and work to be done.
Directories standing for projects and other units of work profit greatly from notes outlining the goals, work to be done, expected events and whatever I need to remember for a variable amount of time.