I don't know, Stan.... Is that a manufactured bone for the specific purpose of whapping the crap out of antelope skulls, (That would be a tool) or simply just another bone Harry picked up because it was handy when he had his mental tirade over yet another evening dinner of nuts and berries?
Somethin' to ponder, fer sure...
Now that Ryan is back in the saddle, and jumping boulders and off-roading on the Rubicon, we can get back to the matter at hand: what constitutes a tool.
To answer El Gordo's Gordian Knot (I've been waiting a while for that one): Stanley Kubrick's 1:45 minute long "ape" scene in "2001" aside, and the inference that Bonzo the Chimp's whapping-bone is just a short little skip to deep space exploration-- at Stanistan U, that head-banging femur would not be a tool. This is not to say that chimps aren't curious little monkeys-- just that if a crow can do it, it's not a tool. If a bird uses a stick to fish out garbage, it doesn't put him on par with me in my shop
... or maybe it does. The bird doesn't crack his head open on every sharp surface within striking distance, nor does he smash his little crow feet when his stick slips off the garbage.