To stifle this thread, the DM has ultimate say in what constitutes as
"the perfect tool for the job" with regards to masterwork tool sets.

If the DM says it's OK, you get the bonus. If not, you don't.

Personally, I think it's just easier to err on the side of caution,
and only purchase those tools sets that are listed in the PHB or other
approved sources.

--
Chris Tulach
LIVING GREYHAWK Circle
Iuz's Border States