[Zope-CMF] Development Philosophy & Architecture Questions

[Norfleet, Sheppard S.]

I am facing the prospect of developing custom portal content.  After
spending some time looking at the CMFDefault product I have a question. 

When should one create a tool as opposed to a portal content type?  Other
than the obvious difference in the nomenclature one could write in code in a
portal content type that should be placed into a tool instead; for instance
version control for content types.  Should one create a new version
controlled document(file) content type, or make a tool that performs version
control on an existing type.

Regards

Sheppard Norfleet