Conciseness

The core phases are lean and imperative, assume Claude's competence (e.g., "A fixed sleep is not a readiness check"; no explanation of what accessibility or WCAG is), and pack dense, useful constraints into single lines. The generic "Limitations" boilerplate ("Do not treat the output as a substitute for environment-specific validation, testing, or expert review") is minor padding that could be trimmed, which fits the 'efficient; minor instances of over-explanation' anchor rather than the every-token-earns-its-place anchor above.

Actionability

Specific, actionable directives throughout — separate local ports, "wait for a deterministic ready selector", "Keep private snapshots in a fresh owner-only directory", verbatim selectors with "file:line (symbol)", "never fabricate" — plus a concrete report template. It contains no executable commands, but that is explicitly justified ("This package does not bundle the CLI or browser... do not invent commands when integration is unavailable"), and per the scoring notes an instruction-only skill is not penalized for lacking code when the guidance is actionable. It still falls short of the copy-paste-ready anchor 5.

Workflow Clarity

A clear three-phase sequence (establish isolated snapshots → report → tear down) with explicit validation checkpoints: "verify which revision each page actually serves", "A fixed sleep is not a readiness check", "Never promise full restoration without verifying file status and content", and "verify with the same controlled baseline". It lacks explicit validate→fix→retry feedback loops, so it matches the 'clear sequence with most checkpoints present; minor validation gaps' anchor rather than the feedback-loops anchor. The destructive/batch cap does not apply since the skill is explicitly report-only ("Don't edit").

Progressive Disclosure

The body is under 50 lines with no bundle files and no content that belongs in a separate file — the report template is small and appropriately inline. Sections are well organized (When to Use / three numbered phases / Gotchas / Limitations), and per the rubric guideline a sub-50-line skill with no need for external references scores 5 on well-organized sections alone.

Specificity

The description lists multiple specific concrete actions: "Diff a live page's accessibility violations against a baseline", "by default compares uncommitted changes (stash-based)", "pass --branch [<name>] to diff against a branch", "Reports only new violations introduced, violations fixed, and pre-existing count", and "Use `scan` for a full audit with no diffing". Coverage spans the default mode, the branch mode, the exact output contents, and the sibling skill, so it matches the comprehensive anchor rather than the 'minor gaps' anchor below.

Completeness

The 'what' is explicit and concrete, but there is no "Use when..." clause or equivalent trigger guidance for invoking this skill — "Use `scan` for a full audit with no diffing" is a pointer to the sibling skill, not a when-to-use trigger. Per the rubric guideline, a missing 'Use when' clause caps completeness at 3; the 'when' is only weakly implied by the 'what', which fits the score-3 anchor rather than the score-4 anchor that requires both to be present.

Trigger Term Quality

Good natural keyword coverage ("accessibility violations", "diff", "baseline", "branch", "audit", "scan") that users would plausibly say, but common synonyms such as "a11y", "WCAG", "contrast", or "screen reader" are absent. This matches the 'good keyword coverage; a few natural terms missing' anchor rather than the comprehensive-synonyms anchor above.

Distinctiveness Conflict Risk

It carves out a clear niche (diffing accessibility violations between two revisions of a page) and even differentiates its own sibling mode ("Use `scan` for a full audit with no diffing"), so it is unlikely to trigger the wrong skill. This matches the 'clear niche with distinct triggers; minimal conflict risk' anchor; the neighboring anchor would require overlap risk with related skills, which is absent.