The body is lean with no concept-padding or boilerplate; every line states a rule, path, format, or constraint and assumes Claude's competence, matching the lean-and-efficient anchor.

Gives concrete executable guidance: a precise storage path ("{state-dir}/perf/baselines/<version>.json"), overwrite policy, required record fields, and an explicit output format block.

Although rule-based rather than step-sequenced, this is a simple single-purpose skill whose single action (persist/overwrite one baseline per version) is unambiguous, so it qualifies for a 3 under the simple-skills note; no destructive batch loop requires a validation checkpoint.

Well-organized sections (Required Rules, Output Format, Constraints) with a single one-level reference to docs/perf-requirements.md as the canonical contract; under 50 lines with no nested bundle references, satisfying the simple-skills exception.

Names the domain and several actions ("managing perf baselines, consolidating results, or comparing versions", "one baseline JSON per version") but stays at the domain level rather than enumerating multiple granular concrete operations like the 3-anchor example.

Explicitly states what it does ("Ensures one baseline JSON per version") and when to use it via a clear "Use when..." trigger clause, satisfying both halves.

Includes relevant natural terms ("perf baselines", "comparing versions", "consolidating results") but coverage is moderate and misses common variations that would push it to the 3-anchor breadth.

The perf-baseline niche has distinct triggers and is unlikely to fire for unrelated skills, matching the clear-niche anchor.