Assuming that the tool tips will be more or less the same as AIC I highly recommend going with a sans-serif font for the actual descriptions, something like Helvetica, Century Gothic, or if you want something with a little more weight to it Franklin Gothic Medium.
As much as I love Times News Roman, the serif on it and others makes them quite hard to read from a computer screen for blocks of text. They'd make a good title or heading font, but I'd leave the actual descriptions as something else.
I'm a simple man of simple tastes: (note: I took these stats from a super old screenshot... it was all I had around at work, heh)
Option 1 (Times New Roman 12pt Header, Centrury Gothic 10pt Body)
Option 2 (Franklin Gothic Medium 12pt Header, Centrury Gothic 10pt Body)
as much as I'd love for things to be at 12pt so I could read them, I think that might be too big for a game though, you'd run out of real estate too quickly. Realistically it would probably be like 8pt fonts
