Let's see here..ah yes the definition of theft:
| 1. |
criminal law the dishonest taking of property belonging to another person with the intention of depriving the owner permanently of its possession |
See that word permanently? I would hardly call taking a tool back after it is used theft, more like borrowing. Besides, if I buy a tool, thinking it is too expensive for what I am using it for, or it is a combination of being too expensive and not exactly the right tool for what I want, and then use it and take it back, there is nothing wrong with that. That is what a return/exchange policy is in place for.

But to each his own I guess....