Conciseness

The body teaches nothing Claude already knows — the anomaly and anti-pattern tables are dense, and code comments carry non-obvious information ('a wait that times out fails the test instead of hanging'). Minor trimmable instances keep it below lean: the version-specific claim "ran 5/5 green on PostgreSQL 16 with psycopg 3" and a few redundant inline comments. Not 3, since there is no padded explanation or concept teaching anywhere.

Actionability

The skill provides a complete, copy-paste-ready pytest file — imports, schema fixture, two-connection harness with timeouts, four anomaly tests, and a retry wrapper — plus the exact invocation `TEST_DSN=... pytest tests/db/test_isolation.py`. Fully executable and covering the common cases, matching the top anchor; not 4 because there are no gaps in executability.

Workflow Clarity

Steps 1–4 are clearly sequenced, and Step 4 is an explicit validation checkpoint checklist ('must fail when you raise the isolation level by one step. Try it.'). Feedback loops are present throughout (fixture asserts starting counts, hang detection, throwaway-database warning for the destructive drop/recreate), so the destructive-operation cap does not apply. Not 4: validation is explicit and built in as a dedicated step with mutation-style checks.

Progressive Disclosure

The bundle's single reference, references/per-database.md, exists and is well-signaled at three points ('Other databases differ', the anti-patterns table, and the References list), exactly one level deep with no nesting. Database-specific differences are appropriately split out while the core test content stays in SKILL.md, and section navigation is easy. Not 4: there are no organization gaps or buried references.

Specificity

"Tests which anomalies each level prevents (dirty, non-repeatable and phantom reads, write skew) in PostgreSQL, MySQL and SQL Server" names the action concretely with enumerated anomaly types and three databases, matching the 'several specific actions; minor gaps' anchor. It is not 5 because the capability set reduces to a single verb ('tests') rather than multiple distinct actions, and not 3 because the enumeration is far more concrete than '1-2 concrete actions'.

Completeness

It explicitly answers both: what ("Tests which anomalies each level prevents… in PostgreSQL, MySQL and SQL Server") and when ("Use when two concurrent database transactions can touch the same rows… or before changing a default isolation level") with concrete trigger phrases, exactly matching the anchor-5 example. Not 4, because the 'when' clause is fully explicit and specific rather than improvable.

Trigger Term Quality

Natural user phrases are comprehensively covered: "balance debits, seat bookings, stock counts", "isolation level", "concurrent database transactions", all four anomaly names, and all three database names — synonym-level coverage matching the top anchor. A 4 would require noticeable missing natural terms, which is not the case here.

Distinctiveness Conflict Risk

The isolation-level anomaly-testing niche is clear and distinct, but "two concurrent database transactions can touch the same rows" has minor overlap risk with closely related concurrency skills (race-condition, deadlock, locking). Fits 'mostly distinct; minor overlap risk' better than the 'minimal conflict risk' of 5.