Conciseness

Every line carries non-obvious, repo-specific knowledge — e.g. 'Model snapshots use typeof(Dictionary<string, object>) (property bag format), not the actual CLR type' and exact test file locations. No padding and no explanation of concepts Claude already knows; clear match to anchor 5.

Actionability

Guidance names concrete APIs with parameters ('process its model with SnapshotModelProcessor.Process(..., resetVersion: true)', 'MigrationsModelDiffer.GetDifferences()') and exact test paths. Minor gaps keep it below anchor 5: 'derive a concrete old ModelSnapshot' and 'use ModelBuilder calls without conventions' are high-level directions without a skeleton test example.

Workflow Clarity

The Pipeline section sequences both add and apply flows, and the regression recipe is ordered (derive old snapshot → process → compare → verify) with an explicit checkpoint: 'The regression succeeds only when the resulting operation list is empty.' Minor gap versus anchor 5: no error-recovery branch for when the operation list is non-empty.

Progressive Disclosure

The skill is under 50 lines with no bundle files needed, and content is cleanly organized into Pipeline, Model Snapshot, and Testing sections. Per the simple-skill guideline, well-organized sections alone warrant anchor 5.

Specificity

The only capability statement is the generic noun phrase 'Implementation details for EF Core migrations' — no concrete actions are described. The enumerated class names (MigrationsSqlGenerator, HistoryRepository, the Migrator) add concrete coverage areas but serve as triggers, not actions, so this falls between the 'names domain with minimal actions' and 'lists several specific actions' anchors.

Completeness

Both parts are explicitly present: 'Implementation details for EF Core migrations' answers what, and 'Use when changing MigrationsSqlGenerator, model diffing, migration operations, HistoryRepository, the Migrator or related classes' answers when with concrete trigger phrases. Not anchor 5 because the 'what' names a topic rather than describing concrete actions.

Trigger Term Quality

'MigrationsSqlGenerator, model diffing, migration operations, HistoryRepository, the Migrator' are natural phrases a developer working in this codebase would say. Common variations like 'scaffold a migration', 'model snapshot', or 'GetDifferences' are missing, keeping it below comprehensive coverage (anchor 5) but clearly above 'some relevant keywords' (anchor 3).

Distinctiveness Conflict Risk

The description carves out a clear niche — EF Core migrations internals with specific named classes — so it is highly distinguishable from other skills and unlikely to trigger for the wrong one. Clear match to anchor 5.