Video Spec Builder

We fed it a deliberately lazy brief — “a promo, ten-odd seconds, three or four shots, for Douyin” — with five answers planted in it that the skill itself says it will not accept.

It came back with a twenty-second vertical spec: twelve shots across nine sections, every shot timed to 0.1s, every visual element named from a real component ID. We then wrote a checker that turns the skill’s own pre-delivery checklist into an executable gate. Twenty checks, twenty passes.

What it is

A conversational spec builder. The selling point is not generation — it is interrogation discipline: it refuses adjectives and pushes every requirement down to shot granularity before it writes anything. Ask for “something cinematic” and it will ask what that means in seconds and frames.

It ships a catalogue of 69 visual components, each with a “when to use / when not to use” note. We counted them — the number in the description is accurate. Writing our spec, all twelve shots landed on real component IDs, because inventing one would contradict the catalogue’s own descriptions.

What we found running it

Conflict detection only exists in iteration mode. Our brief carried a hard contradiction: Douyin is a hook-type platform where the rules require 8–15 shots at 0.8–2.0s each, and the brief asked for 3–4 shots over a dozen seconds — which works out to 4.5s per shot, a documentary pace the rules explicitly forbid for that platform. Nothing in the 0-1 flow is assigned to catch this. It surfaces only if the agent happens to open the pacing rules on its own.

A hard constraint lives only in the references. Narration is bound to a words-per-second band, and our first draft fell under it — but the constraint appears nowhere in SKILL.md. You find it only by reading the pacing rules, which the skill suggests reading “when discussing pacing” — not when writing shots.

Neither is a defect in the output. Both are places where the discipline depends on the agent being thorough rather than on the skill enforcing it, so we wrote the gate ourselves.

Related

For prompting a video model once the spec exists, see Seedance 2.0 Prompting.

Installing

Not ours — install from the source repository. MIT, and it costs nothing to run: no API keys, no paid models.