When I decide about a tool/language (I have learned now dozens) I just think in the HARDEST task that I could possible anticipate. Also, I do some basic stuff.

When I decide about a tool/language (I have learned now dozens) I just think in the HARDEST task that I could possible anticipate. Also, I do some basic stuff. In my case, I try to see how well is to interface with RDBMS. I try to do it with them and then decide. So, in short, build a mental "benchmark" that is representative to help to decide if X is right for you