Under ideal circumstances, how easily should raw chicken cut when using a sharp knife?
If you're picking up a pre-packed chicken in a supermarket, there will be information you cannot access or use - the variety of bird, its age, its diet etc, so what you are left with is a simple rule-set.

The bigger it is, the tougher it is.

Take chicken breast...
A single chicken breast of 150g should be tender. One at 300g won't be. So, avoid the bulk packs that appear to be better value; also check the breast is whole &amp; hasn't been trimmed to look like a smaller one than the bird it came from.

Also avoid the supermarket's sneaky trick - "Mini-fillets"
These look like very small whole breast pieces so your first impression would be that they ought to be tender. In actual fact they have been torn out of the centre of much larger breasts &amp; are often tough as old boots.