Rational is $$$$.
Ive used ERWIN/3.52 and Sybase PowerDesigner.
Sybase is the best tool I think.
Both ERWIN and Sybase support VFP DBCs.

IF your project is big or will be multi-developer
I would highly recommend a database Design Tool like these.

I learned on ERWIN cause it was cheapest at the time (1999)
But ERWIN/ModelMart are very limited in features compared to Rational/Sybase.
Sybase keeps updating theirs every few months it seems, and you can buy it in pieces.

Robot is a testing Tool.
Not sure if it tests fox SCX files, doubt it.

http://www.sybase.com/detail_list/1,6902,2650,00.html