I built a Claude Code skill that refuses to render a 3D explainer unless its numbers match the published ones

You ask for an exploded view of a real thing (a lock, a Rubik's cube, WinRAR, React). The agent looks up the numbers and tags each one SPEC / MEASURED / DERIVED / ESTIMATED with its source. A gate script compares the model with what is published, and if it disagrees, nothing renders. Examples of what the gate checks: a pin tumbler lock must put all five splits on the shear line with the right key; Enigma must reproduce the published test vector (AAAAA becomes BDZGO); a model of React's rules must predict the 1 of 8 DOM nodes the real React 18.3.1 touches. The part that worked for me as a skill author: a gate the agent cannot argue with, and testing the skill with fresh sessions that know nothing about it, then fixing everything they tripped over. Output is a 30 s film with sound, an interactive viewer and an STL/GLB. Built with Claude Code (three.js in a headless browser + ffmpeg). Limits: films need a GPU, I have not tried macOS, and the gate checks the model against the…