Conciseness

The body is lean — compact metric lists with targets ("LCP… target < 2.5s", "Bundle… target < 200KB gzipped"), one-line rationales ("Git-tracked so the team shares baselines"), and no explanation of concepts Claude already knows. Every section earns its tokens, matching the 5 anchor. Not a 4 because there is no over-explanation to trim.

Actionability

Modes 1–3 put plain-language step lists inside code fences ("Navigate to each target URL", "Hit each endpoint 100 times", "Measure: p50, p95, p99 latency") with no executable command, script, or concrete tool invocation — pseudocode with missing key details, matching the 3 anchor. Not a 4 because the gap is not minor: only Mode 4 has real commands ('/benchmark baseline', '/benchmark compare'); not a 2 because the specific metrics, numeric targets, and comparison workflow are concrete guidance.

Workflow Clarity

Sequences are present and clearly separated by mode, but validation checkpoints are absent: no repeat-run/outlier handling for the 100-request batch in Mode 2, no environment controls (cache, cold vs. warm) before measuring, and no verify-the-baseline step before comparing — 'sequence present but checkpoints missing or implicit', matching the 3 anchor. The batch-operation guideline (100 endpoint hits with no variance validation) also caps this at 3. Not a 4 because the comparison verdict table is the only checkpoint and it appears after measurement, with no error-recovery loop.

Progressive Disclosure

Sections are well-organized (When to Use, four modes, Output, Integration) and no content is misplaced since there are no bundle files and nothing requires external navigation — matching the 4 anchor ('good structure; most content appropriately placed; minor organization gaps'). Not a 5 because the body is ~88 lines (past the under-50-line simple-skill exception) and the per-metric target tables and comparison methodology are inlined where a one-level reference could carry them; not a 3 because nothing that clearly belongs in a separate file is inlined and no references are buried.

Specificity

Quotes like "Measure performance baselines and detect regressions across browser Core Web Vitals (LCP, INP, CLS, page weight), API endpoint latency percentiles, and build/test feedback times" list multiple concrete actions with comprehensive coverage, matching the 5 anchor ('multiple specific concrete actions; comprehensive coverage'). It is not a 4 because there are no minor gaps — the modes, storage location ('git-tracked .ecc/benchmarks JSON'), and comparison behavior are all named.

Completeness

Both halves are explicit: the 'what' ("Measure performance baselines and detect regressions across… Core Web Vitals… API endpoint latency percentiles… build/test feedback times, with before/after comparison") and the 'when' ("Use when checking page speed, responding to 'it feels slow' reports, verifying launch performance targets, or comparing stack alternatives") — concrete trigger phrases attached to a clear capability list, exactly the 5 anchor. Not a 4 since the 'when' clause needs no further specificity.

Trigger Term Quality

Triggers such as "checking page speed", "'it feels slow' reports", and "verifying launch performance targets" are natural user phrases, but common synonyms like "benchmark", "page load time", "profile", or "performance regression" are missing — good coverage with a few natural terms absent, which matches the 4 anchor. Not a 5 because synonym/variation coverage is incomplete.

Distinctiveness Conflict Risk

The description stakes out a clear niche (performance measurement/benchmarking) with distinct triggers, but "comparing your stack against alternatives" could fire on general architecture or tech-selection requests that aren't performance-focused — minor overlap risk with closely related skills, matching the 4 anchor. Not a 5 because of that broad trigger; not a 3 because the core triggers (page speed, 'it feels slow', launch performance targets) are clearly specific to this skill.