Conciseness

The bulk is genuinely useful, executable code, so it is mostly efficient — but several sections are unnecessary: the "You are an expert" role preamble, "Key Components" explaining what buckets/objects are, the "Complete Setup Example" repeating four RLS policies verbatim from section 5, and a closing "Summary" that restates the table of contents. This fits anchor 3 (mostly efficient, some tightening possible) better than anchor 2, whose padding dominates the content.

Actionability

Nearly all examples are concrete, copy-paste-ready JavaScript/TypeScript/SQL covering the common cases (upload, download, list, signed URLs, RLS policies). Minor gaps keep it below anchor 5: the signed-upload example uses an undefined `bucketName` variable, the tus example's endpoint host (`${projectId}.storage.supabase.co`) is inconsistent with the Uppy example's (`${projectId}.supabase.co`), and the Uppy snippet pins a CDN version (v3.6.1) with a placeholder token.

Workflow Clarity

The body is a well-ordered API catalog rather than a sequenced workflow, and it contains no validation checkpoints for risky operations: "Delete Bucket", "Empty Bucket", and bulk "Remove Files" appear with no verify-before-destructive guidance, and RLS policies are given without a check-that-RLS-is-enabled or test-the-policy step. Per the rubric, missing validation for destructive/batch operations caps this at 3; the numbered section structure keeps it from scoring lower.

Progressive Disclosure

The body has clear structure (9 numbered sections with headers), but it is a ~720-line monolith with no bundle files at all: the full tus/Uppy resumable-upload guides, the complete RLS policy catalog, and the Edge Function proxy are all inlined content that clearly belongs in separate reference files. This matches anchor 3 (some structure, content that should be separate is inline) — better organized than anchor 2's header-less dump, but without any of the well-signaled references that anchor 4+ requires.

Specificity

The description lists several specific capability areas — "bucket management, file operations, URL generation, and RLS policies" plus concrete triggers like "generating signed URLs", "handling resumable uploads, image transformations" — but the 'what' half relies on category nouns ("file operations", "bucket management") rather than enumerated concrete actions like the anchor-5 example, and "Expert guide for" is mild filler. It sits noticeably above the midpoint, matching anchor 4 rather than 5.

Completeness

It explicitly answers both questions: 'what' via "Expert guide for Supabase Storage including bucket management, file operations, URL generation, and RLS policies" and 'when' via the explicit clause "Use when working with file uploads/downloads, creating public or private buckets, generating signed URLs, implementing storage RLS policies, handling resumable uploads, image transformations". This matches anchor 5's what-and-when-with-concrete-triggers pattern; it is clearly above anchor 4, whose 'when' is less specific.

Trigger Term Quality

Natural trigger phrases a user would actually say are comprehensively covered: "file uploads/downloads", "creating public or private buckets", "generating signed URLs", "storage RLS policies", "resumable uploads", "image transformations", with the domain name "Supabase Storage" repeated and a catch-all "any Supabase Storage-related tasks". No relevant file extensions exist for this domain, so the synonym-coverage bar of anchor 5 is met.

Distinctiveness Conflict Risk

"Supabase Storage" is a clear niche with distinct, storage-scoped triggers (buckets, signed URLs, storage RLS) that would not fire for unrelated skills; only trivial overlap with a hypothetical general Supabase skill exists, matching anchor 5's minimal conflict risk.