Conciseness

The ~30-line body is a pure index: each entry is one line of scope ("Data types, constraints, indexes, JSONB patterns, partitioning, and PostgreSQL best practices") plus a bolded use-when pointer, with zero explanation of concepts Claude already knows. This matches the lean 'every token earns its place' anchor; nothing to trim.

Actionability

The body is an instruction-only router and its guidance is concrete: real paths ("references/design-postgres-tables.md"), per-reference scopes, and a bolded directive per entry ("Use for any general table/schema design task"). Not a 5 because there is no inline quick-start example for the most common task (e.g., a basic CREATE TABLE / index pattern), so a user must always open a reference file before acting — 'minor gaps' at anchor 4.

Workflow Clarity

"How to Use" gives an unambiguous three-step sequence: "1. Identify which reference matches the user's task... 2. Load the reference file... 3. For tasks spanning multiple areas..., load multiple references as needed." This is a single-purpose routing skill with no risky operations, so the simple-skill exception applies and the single action is unambiguous. A 4 would require missing checkpoints, but none are needed for non-destructive reference loading.

Progressive Disclosure

All nine referenced paths resolve to real files one level deep, grouped under clear category sections with per-reference use-when signals — close to the anchor-5 pattern. Not a 5 because the actual bundle has minor organization gaps: three reference files (backfill-strategies.md, complete-example.md, validation-queries.md) are not navigable from SKILL.md, and references/schema-exploration/ contains a further nested references/ directory, introducing 2-level depth for that entry.

Specificity

The description lists many concrete actions — "Explore an existing PostgreSQL database", "Design or modify PostgreSQL tables, schemas, or data models", "Choose data types, constraints, indexes, or partitioning strategies", "Set up TimescaleDB hypertables", "Plan or execute safe schema migrations with zero downtime" — covering the full domain comprehensively. Not a level below because 4 allows 'minor gaps in coverage' and no significant capability area is missing.

Completeness

It explicitly answers both questions: what ("Use this skill for any PostgreSQL database work — table design, indexing, data types, constraints, extensions..., search, and migrations") and when ("**Trigger when user asks to:**" followed by nine concrete trigger phrases). This is the anchor-5 pattern of a clear 'what' plus explicit 'Use when' triggers; a 4 would require the 'when' to be less explicit, which it is not.

Trigger Term Quality

The keyword list ("PostgreSQL, Postgres, SQL, schema, table design, indexes, constraints, pgvector, PostGIS, TimescaleDB, hypertable, semantic search, hybrid search, BM25, time-series, migration") includes the natural Postgres/PostgreSQL synonym and most terms a user would say. Not a 5 because common natural phrasings such as "database design", "query optimization / performance tuning", "vacuum", or "SQL queries" are absent, which is the 'a few natural terms missing' anchor.

Distinctiveness Conflict Risk

Highly specific niche markers ("pgvector", "PostGIS", "TimescaleDB", "hypertable", "BM25") make this mostly distinct with minimal conflict risk against unrelated skills. Not a 5 because generic keywords like "SQL", "schema", and "migration" create minor overlap risk with generic SQL/non-Postgres database skills — the anchor-4 'minor overlap risk with closely related skills' case.