Based on a dogs shape and coat, you can pretty easily determine the breed families in it. It's important to know since dog breeds are much more diverse due to their history with humans around the world—most have jobs bred into them. So it's still good to know if your dog has breeding in it that thrives on exercise or fetch jobs or that sort of thing. Most of those little dogs are for hunting small vermin and are savage fuckers, for example.

Cats it's mostly one size fits all with a random roll on personality stats.