Conciseness

The body is very lean (~15 lines) with zero concept explanation, but it is not perfectly token-efficient: the opening paragraph repeats the frontmatter description verbatim, and the billing constraint is stated three times ("bills the Ads agent" in the intro, "bills the agent" in Run, "bills the Ads agent" in Contract). Anchor 4 ("efficient; minor instances... that could be trimmed") fits better than anchor 5's "every token earns its place".

Actionability

The Run section gives a real, verified command — "gen_music.py --prompt '...' --duration 10 --out music.m4a" — whose flags match the bundled scripts/gen_music.py. It stops short of anchor 5 ("fully executable; copy-paste ready"): the prompt is an ellipsis placeholder whose source ("the template recipe") is never made executable, and the command omits the scripts/ path. It is above anchor 3 because the command is genuine and runnable once inputs are supplied.

Workflow Clarity

This is a simple single-action skill, and the action is mostly unambiguous: run gen_music.py with recipe-supplied prompt and length. It does not reach 5 under the simple-skill exception because the single action is not fully unambiguous — how to obtain the "template recipe (DB)" values is never stated, and there is no checkpoint verifying the generated bed (duration/loudness) after a paid call. It is above anchor 3 because the sequence that is written is clear and correct.

Progressive Disclosure

Under 50 lines with no need for external reference files, and the body is split into well-organized sections (Run, Contract) that correctly point at the actual bundle: both referenced files exist (scripts/gen_music.py, scripts/media_proxy.py) and gen_music.py imports media_proxy as documented. Per the rubric's simple-skill note, this earns the top anchor; the only nit — the Run command not carrying the scripts/ prefix — is too minor to drop it to anchor 4.

Specificity

The description lists multiple concrete actions covering the full capability: "Generate an instrumental music bed via ElevenLabs Music", "Trims any sparse intro, loudnorm, fades the tail", plus routing and parameter sourcing ("Prompt + length from the template recipe"). This matches the anchor for multiple specific concrete actions with comprehensive coverage; it is above anchor 4 because no meaningful action in the skill's scope is left unmentioned.

Completeness

Both parts are explicit: the "what" is a concrete capability statement (generate, route, trim, loudnorm, fade) and the "when" is an explicit trigger clause — "Use for the music layer of any video-ad format." This mirrors the anchor-5 example structure (what + "Use when/for..." with a concrete trigger phrase), so it is not capped at 3 for a missing trigger clause nor held at 4, since the when-clause is specific rather than generic.

Trigger Term Quality

Good natural keyword coverage: "instrumental music bed", "music", "ElevenLabs Music", "music layer", "video-ad". It falls short of anchor 5 because common synonyms users would actually say — "background music", "soundtrack", "score", "BGM" — are absent, matching anchor 4's "good keyword coverage; a few natural terms missing".

Distinctiveness Conflict Risk

It carves a clear niche — instrumental music-bed generation for video-ad formats via ElevenLabs Music with proxy billing — with triggers unlikely to collide with other skills. This matches anchor 5 ("clear niche with distinct triggers; minimal conflict risk"); anchor 4 would require noticeable overlap with a closely related skill, which is not present.