Conciseness

The body is lean: a terse 'When to Apply' bullet list, a compact 8-row category/priority table, and a short pointer to reference files. It explains nothing Claude already knows and contains no padding, matching 'Lean and efficient; assumes Claude's competence; every token earns its place'.

Actionability

The only executable instruction is 'Read individual rule files', backed by a prefix table and three example paths (references/query-missing-indexes.md, query-partial-indexes.md, _sections.md). No SQL or commands appear in the body itself, and only 3 of the ~35 actual rule files are named, so a user with an RLS or pooling problem has no direct file to open — this is 'Some concrete guidance but incomplete ... missing key details' rather than the mostly-executable level-4 anchor.

Workflow Clarity

'How to Use' implies a loose process (pick a category, read its rule files, apply the correct SQL patterns) but never sequences it as steps, and there are no checkpoints such as verifying the fix with EXPLAIN ANALYZE after applying a rule. This matches 'sequence present but checkpoints missing or implicit'; the level-4 anchor requires a clearly laid-out sequence with most checkpoints present.

Progressive Disclosure

The bundle structure is good: 35 one-level-deep rule files in references/, organized by filename prefix, with the body's priority table mapping categories to prefixes. But navigation is only inferable — the body lists just 3 example files without stating the references/<prefix>-<topic>.md naming pattern, and it points to _sections.md, an internal scaffold file whose own text says 'Take the examples below as pure demonstrative', which should not be surfaced to skill consumers. This is 'Good structure ... references mostly clear; minor organization gaps' rather than the fully navigable level-5 anchor.

Specificity

The description names the domain ('Postgres performance optimization') and a handful of actions ('writing, reviewing, or optimizing Postgres queries, schema designs, or database configurations'), but the core capability phrase 'best practices' is generic and it omits concrete deliverables like index creation, EXPLAIN analysis, or connection pooling setup. This matches the anchor 'Names domain and 1-2 concrete actions, but not comprehensive' more than the level-4 anchor, which expects several listed specific actions with only minor gaps.

Completeness

Both halves are present: the what ('Postgres performance optimization and best practices from Supabase') and an explicit when ('Use this skill when writing, reviewing, or optimizing Postgres queries, schema designs, or database configurations'). It falls just short of the level-5 anchor because the 'what' is abstract — it never says what the skill actually contains (rules, incorrect vs. correct SQL examples, metrics) — leaving the when clause doing most of the work.

Trigger Term Quality

Natural terms users would say are present: 'Postgres', 'queries', 'schema designs', 'database configurations', 'performance optimization', plus the 'Supabase' brand tie-in. A few commonly-said variants are missing (SQL, indexes/indexing, slow queries, connection pooling, .sql), so it fits 'Good keyword coverage; a few natural terms missing' rather than the level-5 comprehensive-synonym anchor.

Distinctiveness Conflict Risk

The Supabase + Postgres framing carves out a clear niche with distinct triggers ('Postgres queries', 'schema designs', 'Supabase'), unlikely to pull in unrelated skills. It is not below this anchor: level 4 is for skills with minor overlap risk against closely related skills, and the explicit Postgres/Supabase scoping keeps conflict minimal.