Conciseness

The body is lean and code-first with essentially zero prose padding — every section is executable snippets with one-line comments — but the 'Quick Reference' table at the top substantially duplicates the 'Basic Queries' section (select/insert/update/delete appear in both). That places it at level 4 (minor instances that could be trimmed) rather than level 5, where every token earns its place.

Actionability

Nearly all examples are complete, executable statements with destructured results and error handling ('const { data, error } = await supabase.from(...)'), covering the common cases: CRUD, filters, ordering, pagination, joins, RLS policies, RPC definition and call, and type generation. The filter-operator fragments (e.g. '.eq('col', 'value')') are API signatures rather than pseudocode, so this is copy-paste ready — the level-5 anchor.

Workflow Clarity

The skill covers destructive database operations (delete, update, RLS policy creation) but includes no validation or error-recovery workflow — snippets destruct 'error' yet nothing instructs checking it before proceeding, and there is no verify-then-retry loop. Per the rubric's explicit cap for destructive/batch/database operations without validation, workflow_clarity cannot exceed 3 even though the material is clearly organized by topic.

Progressive Disclosure

All three referenced bundle files (references/rls-policies.md, query-operators.md, postgres-functions.md) exist, are one level deep, and are clearly signaled in a closing References section with one-line descriptions — good structure. It falls short of level 5 because substantial content duplicated in those files (the Filters section vs query-operators.md, the RLS section vs rls-policies.md) is fully inlined rather than split, and the Quick Reference table adds a third copy of basic CRUD.

Specificity

The description lists multiple concrete actions — 'queries, CRUD operations, RLS policies, and PostgreSQL functions' — covering the domain comprehensively with no filler, matching the level-5 anchor of multiple specific concrete actions. It does not fit level 4 because coverage is not merely 'minor gaps'; the four named action areas span the skill's whole scope.

Completeness

It explicitly answers both: what — 'Supabase database operations including queries, CRUD operations, RLS policies, and PostgreSQL functions' — and when — 'Use when querying tables, managing data, implementing RLS, or writing database functions'. Both are concrete and explicit, matching the level-5 anchor exactly; level 4 would require a weaker or less specific 'when' clause.

Trigger Term Quality

Trigger phrases 'querying tables, managing data, implementing RLS, or writing database functions' are natural user phrasings, but common variations are missing — no 'Postgres', 'SQL', 'row-level security' spelled out, or 'select/insert/update data'. This matches level 4 (good coverage, a few natural terms missing) rather than level 5, which requires synonyms and variations.

Distinctiveness Conflict Risk

'Supabase' names a clear niche, but 'PostgreSQL functions' and 'querying tables' could also fire on generic Postgres/SQL requests, giving minor overlap risk with closely related database skills — the level-4 anchor. Not level 5: distinctiveness relies on the platform name while the action terms themselves are generic; not level 3: the Supabase/RLS framing is far more specific than 'Works with document files'.