Conciseness

The body is dense rather than padded: it assumes engine knowledge and devotes nearly every sentence to non-obvious lock/rewrite facts, version gates, or classification directives, so it is well above the 'noticeably verbose' anchor. It falls short of anchor 5 only because long verbatim manual quotations (e.g. the multi-sentence ADD FOREIGN KEY and DROP COLUMN quotes) could be trimmed to the operative clauses without losing decision value.

Actionability

For an instruction-only skill the guidance is fully executable: an eight-category table with SQL examples, per-check verdicts ("Classify a plain CREATE INDEX on PostgreSQL as category 3: Warning with no size signal, Critical on a large table"), a copy-paste-ready output table and count block, and a worked example covering five common statement types in the reference file. This matches "specific examples cover the common cases".

Workflow Clarity

Steps 1-4 are explicitly sequenced with validation checkpoints: inputs must be recorded or marked "unknown" before classifying, the output requires a basis per row ("a row with a severity and no basis is not a classification"), and the count block tracks "Unclassifiable statements". Error-recovery paths exist (classify per-engine and report the worst case when the engine is unknown; report version-gated severity as a range), and the anti-patterns section acts as a checklist, matching the anchor-5 combination of explicit validation, feedback loops, and checklists.

Progressive Disclosure

The procedure lives in SKILL.md under clear headers, while the consolidated per-engine lock/rewrite tables and a full worked example are split into a single reference (references/engine-quick-reference.md) that exists, is one level deep, matches what the body says it contains, and is clearly signposted in the "Per-engine quick reference" section. This matches the well-signaled one-level-deep reference structure of anchor 5.

Specificity

"Classifies each statement (additive, locking, breaking, data-loss) by lock and rewrite" is a concrete action, and the enumerated operations ("rename or drop a column, add NOT NULL or a default, add an index or foreign key, change a type") are specific. It stops short of anchor 5 because there is one core action (classification) applied to enumerated inputs rather than multiple distinct concrete actions like the anchor's extract/fill/merge/convert list.

Completeness

Both halves are explicit: the trigger "Use whenever someone asks if a database migration is safe to run in production" with concrete triggering operations, and the what — "Classifies each statement (additive, locking, breaking, data-loss) by lock and rewrite". This clearly matches the anchor that answers both what and when with concrete trigger phrases, not the anchor-4 case where the 'when' could be more explicit.

Trigger Term Quality

Phrases a user would naturally say are present: "if a database migration is safe to run in production", "drop a column", "add an index", "PostgreSQL or MySQL". A few common variations are missing ("schema change", "ALTER TABLE", "deploy/roll out a migration"), which matches "good keyword coverage; a few natural terms missing" rather than the comprehensive synonym coverage of anchor 5.

Distinctiveness Conflict Risk

Production migration-safety classification for PostgreSQL/MySQL is a clear niche with distinct triggers, and the description is narrowly about classification (not authoring or running migrations), so conflict with adjacent migration skills is minimal. It fits the "clear niche with distinct triggers" anchor; anchor 4 would require identifiable overlap with closely related skills, which is not the case.