humanoid

The humanoid avatar type: a body with two legs, a spine, a head and one or two arms.

qualify(structure) finds the body from the skeleton's shape, so any bone naming works (Mixamo, Unity, VRM, CATS, Unreal, Synty, or no meaningful names at all):

• The hips are where two mirrored chains reaching the skeleton's lowest point (the legs) branch from a chain rising to its highest point (the spine). A bone above the hips is the root.
• The arms are the two mirrored chains branching sideways near the top of the spine; above that branch the chain continues through the neck to the head.
• A hand is where an arm ends in a fan of fingers; the thumb is the finger set apart from the others.
• A foot is where a leg turns forward; the next bone is the toe base.
• Left and right come from the body's facing (the direction the feet point), never from names.
• A four-legged body declines: its spine runs across the legs, or it leans well off the legs while the legs stand extended and a limb hanging from the chest reaches down toward the ground the feet stand on. A crouching biped leans and reaches low too, on folded legs.

Names only raise confidence and break ties. A name that contradicts the geometry is reported in report.contradictions and does not change the side.

Every other branch is a secondary chain, classed hair, ear or face (on the head), chest (paired, forward, on the upper spine), butt (paired, backward, on the hips), tail (single, backward, on the hips), skirt (a ring of downward chains on the hips), attachment (a single leaf bone such as a prop socket) or other.

A rig that is not a humanoid declines with a one-line reason naming the first requirement it missed. See the avatarType asset type's README for the full result shape.