Conciseness

The ~17-line body is lean: each phase is one line with terse, load-bearing specifics ("no try/catch, fetch only", "Static -> .astro (zero JS)"), architecture details are delegated to `docs/ARCHITECTURE.md` rather than restated, and nothing explains concepts Claude already knows. This matches 'Lean and efficient; every token earns its place'; there is no over-explanation that would justify 4.

Actionability

Concrete guidance dominates: exact directories (`src/modules/[name]/`, `src/islands/`), exact file patterns (`.types.ts`, `.contracts.ts`), and enforceable rules (`client:*`, "zero JS", "fetch only") — fitting 'Mostly executable guidance; concrete code or commands with minor gaps'. It stops short of 5 because "Validate build/check/tests" gives no actual commands and Phase 2's "adapter" is undefined.

Workflow Clarity

Phases 0-6 are clearly numbered and sequenced, with explicit checkpoints ("Validate build/check/tests after each phase", "Ask for approval before each phase") that satisfy the validation requirement for batch/destructive work. It sits between 4 and 5: the explicit error-recovery feedback loop required by the 5 anchor (what to do when validation fails — fix, re-validate, re-approve) is absent.

Progressive Disclosure

The skill is under 50 lines with well-organized sections and no bundle files; the per the simple-skill guideline this can score 5 with just well-organized sections. Architecture detail is correctly pushed out to a clearly signaled one-level reference (`docs/ARCHITECTURE.md`) and nothing that belongs in a separate file is inlined.

Specificity

"runs 6 phases with approval gates" names the domain ("module needs migration to the target architecture") but the only action described is the generic shape of the process — what the phases actually do (structure, types, services, routing, components) is never stated. This matches the anchor 'Names the domain but actions are minimal or generic' rather than 3, which requires 1-2 concrete capabilities; it is also above 1 since it is not pure abstraction.

Completeness

Both parts are present: the what ("runs 6 phases with approval gates" for module migration) and an explicit when ("Use when a complete module needs migration to the target architecture"). It fits anchor 4 — 'when' could be more explicit or specific (it never names the target architecture or concrete trigger phrases) — and does not reach 5, whose example lists multiple concrete trigger phrases and a fuller statement of capabilities.

Trigger Term Quality

Relevant keywords are present ("module", "migration", "complete module") and "Use when a complete module needs migration" is natural phrasing, but common variations are missing: the architecture name ("Astro", which the body targets), and synonyms like "port", "rewrite", or "refactor". This matches 'Some relevant keywords but missing common variations or synonyms'; it falls short of 4's 'good keyword coverage' because the single most distinctive term (Astro) is absent.

Distinctiveness Conflict Risk

"a complete module needs migration" carves out a distinct niche (whole-module migration, gated in phases) that would not collide with unrelated skills, fitting 'Mostly distinct; minor overlap risk'. It is not 5 because "target architecture" is unnamed, so requests to migrate or port something smaller or to a different target could plausibly pull this skill in; it is above 3, whose examples are far more generic.