Conciseness

The body is efficient — platform-specific model-string tables instead of prose, conditional 'Apply if' gates instead of explanation, and no concepts Claude already knows padded in. It sits at the 4 anchor because of minor redundancy: the tool-overtriggering before/after list ("CRITICAL:" → remove, "You MUST..." → "You should...") duplicates the near-identical table in references/prompt-snippets.md and could be trimmed. Not 3 — the padding is isolated, not a pattern; not 5 — the duplication exists.

Actionability

Guidance is mostly copy-paste ready: exact per-platform model strings ('claude-opus-4-5-20251101', 'anthropic.claude-opus-4-5-20251101-v1:0'), the exact beta header to remove ('context-1m-2025-08-07'), and exact wording replacements. It falls short of 5 because step 1 ('Search codebase for model strings and API calls') gives no concrete search command or pattern, leaving the entry action under-specified.

Workflow Clarity

The six-step sequence is clearly ordered and each prompt adjustment has explicit application conditions, but there is no validation or verification checkpoint for what is a batch operation across a codebase. Per the rubric's guideline that missing validation in batch operations caps workflow clarity at 3, this cannot score 4 — 'Summarize all changes made' reports but does not verify (e.g., confirming no residual old model strings or that the code still builds).

Progressive Disclosure

Good structure: the body is an overview with the workflow and lookup tables inline, and detail is correctly pushed one level deep into real, well-signaled files (references/effort.md, references/prompt-snippets.md — both exist and contain the promised content). It is not 5 because content is imperfectly split: the before/after replacement table is inlined in both SKILL.md and the snippet reference, a minor organization gap that fits the 4 anchor.

Specificity

The description lists multiple concrete actions — "Migrate prompts and code", "Handles model string updates and prompt adjustments for known Opus 4.5 behavioral differences" — covering the skill's full scope (string migration plus behavioral fixes). This matches the 'multiple specific concrete actions; comprehensive coverage' anchor; it is not score 4 because there are no meaningful coverage gaps in what the description promises.

Completeness

It explicitly answers both questions: what ("Migrate prompts and code... Handles model string updates and prompt adjustments") and when ("Use when the user wants to update their codebase, prompts, or API calls to use Opus 4.5") with concrete trigger phrasing. This matches the 5 anchor exactly; score 4 would require the 'when' to be less explicit than it is.

Trigger Term Quality

Good natural keyword coverage: "update their codebase, prompts, or API calls to use Opus 4.5" plus the specific model names ("Sonnet 4.0, Sonnet 4.5, or Opus 4.1 to Opus 4.5") users would say. It falls short of the 5 anchor because common synonyms like "upgrade" or phrase variants ("switch to", "move to Opus 4.5") are missing, but it is well above the 3 anchor's 'missing common variations'.

Distinctiveness Conflict Risk

A clear niche (migrating to one specific model version) with distinct triggers (the named model versions) and an explicit boundary ("Does NOT migrate Haiku 4.5"), minimizing the chance it triggers for the wrong skill. Not score 4: no meaningful overlap risk with adjacent skills remains.