Conciseness

The ~26-line body is dense and lean with zero padding: every sentence adds non-obvious expert guidance (e.g., 'A function marked STABLE or IMMUTABLE is not a safety guarantee', 'placeholders cannot replace SQL identifiers in data queries') and none of it re-explains what Claude already knows.

Actionability

The body gives concrete directives ('Check server_version_num first', 'use a read-only transaction and a reasonable statement timeout', 'validate a vetted read-only query with plain EXPLAIN') and delegates executable queries to reference files that verifiably contain complete, copy-paste-ready SQL with consistent $1/$2 placeholder conventions — appropriate and actionable for an instruction-only skill.

Workflow Clarity

A clear 5-step workflow with explicit checkpoints and feedback loops: approval required before data-derived values, 'Ask the user when semantics remain ambiguous', 'If a query fails due to permissions or version differences, report the limitation instead of guessing', and a stop condition ('Stop once you can answer').

Progressive Disclosure

The body is a concise overview with well-signaled, verified one-level-deep references — all 12 linked files exist and match their roles (tables, views, routines, triggers, security, extensions, etc.), with cross-references between siblings explicitly gated ('Follow cross-references only when the question requires them').

Specificity

Names the domain ('Explore an existing PostgreSQL database') and several concrete actions ('Find the relevant objects with read-only pg_catalog queries, then request approval before inspecting data-derived statistics or rows'). A 5 would require a more comprehensive catalog of specific capabilities, while a 3 would undercount the paired query-then-approval actions described.

Completeness

Explicitly answers what ('Find the relevant objects with read-only pg_catalog queries, then request approval...') and when ('Use this skill whenever a user asks for a query or a data-backed answer against an unfamiliar schema...') with concrete trigger phrases, and adds a boundary clause ('Not a schema-design or migration guide').

Trigger Term Quality

Covers natural user phrasings comprehensively: 'asks for a query or a data-backed answer', 'counts, missing or failed records, recent changes', 'where a business concept lives', 'how tables, joins, views, routines, triggers, RLS, or extensions work', plus 'PostgreSQL' and 'unfamiliar schema'. Includes synonyms across the full range of trigger scenarios, so the anchor-4 example of missing natural terms does not apply.

Distinctiveness Conflict Risk

Clear niche with a distinct trigger set and an explicit negative boundary ('Not a schema-design or migration guide'), but 'whenever a user asks for a query' and SQL-writing language overlap with generic SQL-authoring skills, so minor conflict risk remains rather than the minimal risk of a 5.