Conciseness

The ~40-line body never explains concepts Claude already knows (no 'what is SQLite' padding) and every sentence carries project-specific policy such as 'Preserve the established package unless it cannot satisfy a concrete requirement' and 'Keep storage models behind repositories so schema details do not leak into widgets'. This matches the anchor 'Lean and efficient; assumes Claude's competence; every token earns its place' — there is nothing to trim without losing guidance.

Actionability

Directives are concrete — 'inspect `pubspec.yaml`, SDK constraints, the resolved persistence package and version', 'Classify stored state as durable user data, a durable operation, a disposable cache, or reproducible derived data', 'Use temporary databases or directories for deterministic tests' — which fits 'mostly executable guidance with minor gaps'. It is not a 5 because, as an instruction-only skill, it provides no commands or code snippets and leaves the mechanical 'how' (e.g., checking the resolved package version) to the references; it is above 3 because the guidance is specific and followable rather than pseudocode-level.

Workflow Clarity

The sections form a coherent ordered workflow (inspect the project → select storage → model ownership → consult references conditionally → migrate safely → verify) with an explicit verification checkpoint: 'Test first run, reopen, upgrade, failed write, concurrent access, corrupted data, deletion, and offline/online transitions' plus a failure policy ('Never destroy durable user data as an automatic response to migration failure'), so the missing-validation cap does not apply. It falls short of 5 because there is no explicit validate → fix → retry feedback loop in the main body, leaving minor validation gaps — anchor 4 is the best fit.

Progressive Disclosure

The body is a concise overview with three one-level-deep references in `references/`, each clearly signaled with a conditional trigger ('Read [caching policy](references/caching-policy.md) when choosing cache keys, freshness, invalidation, eviction...'), and all three files exist and are substantive. This matches 'Clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation' — the split is exactly along the lines where detail would bloat the overview.

Specificity

'Design or review Flutter on-device persistence, caching, schema migrations, and offline synchronization' names the domain and multiple concrete capabilities (persistence, caching, migrations, offline sync) under two explicit actions (design, review), matching 'Lists multiple specific concrete actions; comprehensive coverage'. It is not 4 because the coverage spans the domain's main pillars with no notable gap and no vague filler.

Completeness

The first sentence explicitly answers 'what' ('Design or review Flutter on-device persistence, caching, schema migrations, and offline synchronization') and the second explicitly answers 'when' with concrete trigger phrases ('Use for preferences, files, local databases, cache lifecycle, or durable queues'). This matches the anchor 'Clearly and explicitly answers both what AND when with concrete trigger phrases'; it is not 4 because the 'when' clause is specific and explicit rather than merely present.

Trigger Term Quality

'Use for preferences, files, local databases, cache lifecycle, or durable queues' contains the natural vocabulary users would say, fitting 'Good keyword coverage; a few natural terms missing'. It is not 5 because common synonyms and ecosystem package names users actually mention (shared_preferences, sqflite, Hive, Isar, sqlite, .db) are absent; it is above 3 because the terms present are the natural phrases, not jargon.

Distinctiveness Conflict Risk

The description carves out a clear niche (on-device persistence in Flutter) and actively disambiguates from siblings: 'route remote transport to flutter-networking and broad threat audits to flutter-security', and 'while preserving the existing package' scopes it against rewrite-style skills. This matches 'Clear niche with distinct triggers; minimal conflict risk'.