This seems like the most important tool for hitters. If you can hit for a good average and maintain decent discipline you should be close to a lock for ML playing time. It seems like Oscar Taveras is the guy. Who else has a 6+ future hit tool in the minors? And decent discipline? So probably not a guy like Baez. Also, is it fair to judge a major leaguers hit tool by his BABIP or XBABIP? It seems like that stat correlates the closest with what is meant by hit tool. So guys that consistently hit for a high babip like David wright, Cano, Pedroia are examples.
List of possible guys: Raimel Tapia, David Dahl, Devon Travis, Wilmer Flores, Arismendy Alcantara, Jorge Bonifacio, Phil Ervin. Mookie betts, Garin Cecchini, Eddie Rosario, Rougned Odor, Jorge Soler, Byron Buxton, Kris Bryant