Conciseness

The body is lean and assumes Claude's competence — every sentence adds non-obvious information ("The question decides the shape", "Persistence is the thing the prototype is _checking_, not something it should depend on", "The main branch keeps only the validated decision"). There is no padding and no explanation of concepts Claude already knows, matching the top anchor.

Actionability

Concrete, executable guidance throughout: specific artifact forms ("a single shareable HTML file (free-play buttons plus tabbed guided walkthroughs)", "several radically different UI variations on a single route, switchable via a URL search param and a floating bottom bar"), concrete run commands ("pnpm <name>", "python <path>", "bun <path>"), and a specific capture procedure. It is not a 5 because no starter scaffold or code snippet is provided for the two artifact types, leaving minor execution gaps.

Workflow Clarity

The sequence is clear: identify the question, pick a branch (with an explicit ambiguity fallback rule and an instruction to state the assumption), apply the six rules, then capture. Checkpoints are mostly present — the branch-selection decision rule acts as an early guard — but there is no explicit validation step confirming the prototype actually answered the question before capture, which keeps it below the 5 anchor.

Progressive Disclosure

The structure is well designed — a short overview that branches to two clearly-signaled, one-level-deep references ([LOGIC.md](LOGIC.md) and [UI.md](UI.md)) — but neither referenced file exists in the skill bundle (no references/, scripts/, assets/, or top-level LOGIC.md/UI.md are present). Per the guideline to score against the actual bundle structure, the branch destinations are dangling, so navigation to the core branch content fails.

Specificity

The description names a concrete action ("Build a throwaway prototype to answer a design question") and enumerates two specific capability scopes ("sanity-check whether a state model or logic feels right", "explore what a UI should look like"), matching the 'several specific actions with minor gaps' anchor. It is not a 5 because it stops short of comprehensively covering what the prototype artifacts are (e.g., the HTML logic demo or multi-variant UI route described in the body).

Completeness

It explicitly answers both questions: what ("Build a throwaway prototype to answer a design question") and when ("Use when the user wants to sanity-check... or explore what a UI should look like") with concrete trigger phrases, matching the top anchor. Not below 5 because neither half is vague or merely implied.

Trigger Term Quality

Natural trigger phrases are present — "prototype", "sanity-check", "whether a state model or logic feels right", "explore what a UI should look like" — phrasings a user would plausibly say. It falls short of the 5 anchor because common synonyms like "mockup", "spike", "proof of concept", or "wireframe" are absent.

Distinctiveness Conflict Risk

The throwaway-prototype niche is clear and the two triggers are distinctive, but "explore what a UI should look like" has minor overlap risk with general UI-design or mockup-generation skills, fitting the 'mostly distinct; minor overlap risk' anchor rather than the minimal-conflict 5 anchor.