Skin weights

Use this when a 2D character (layered parts, or one whole approved image for small motion) needs weighted meshes: auto-weighting a part, diagnosing a fold, leak or rubbery joint, or proving that weights survive the actual motion. It owns the weight field and its evidence. Hierarchy, pivots, art readiness, runtime integration and final acceptance stay with spine-skeletal, which this skill feeds.

Weights are a design decision, not a solver output. The solver interpolates between rigid regions you declare; it cannot know where a joint should bend, what is hidden under a sleeve, or that a beak must stay rigid.

From a one-line request

A short request such as "a pelican riding a bicycle with a fish in its beak, with bone and skin-weight animation" is enough. Before drawing, derive and write down the missing decisions, then show them in the first reply so the user can correct them:

• Contacts from the action. Whatever the body uses must stay on it: a rider's feet on the pedals and hands (or wing tips) on the handlebar, a held object in the hand or beak. Each becomes a two-bone IK chain or a pinned contact with fixed bone lengths.
• Rigid parts. Head, face, beak, hands, feet and boots, hard props (rims, frames, weapons) are one bone each.
• Soft parts. Necks, tails, held animals, cloth ends and tyres get weights. A held object is pinned where it is gripped and loose at its free ends.
• Rhythm. Secondary motion follows the main loop: a rider's head and tail sway once per pedal stroke; bumps add lag.
• Mode. Pick whole-figure or layered parts from the motion size (see the spine-skeletal mode table).
• Evidence by default. Lint, fold audit and surface measures, a fixed-camera GIF and a --bones --constraints overlay. The worked case examples/pelican-bicycle is the reference for these defaults.

Ask only when a choice changes the result and the request cannot settle it, for example which engine will play it.