Conciseness

The body is code-first and assumes competence ("Use modular style… never classic/top-level style for production"), with only minor trimmables: the opening blockquote repeats the description verbatim, the Sequel-over-ActiveRecord rationale appears in both "Key Conventions" and again in "Integration Notes", and a few comments state the obvious ("# Password hashing"). It is below anchor 5 because of that redundancy, but well above anchor 3 since there is no padded prose or explanation of basics.

Actionability

Everything is executable: exact `bundle add` commands, complete copy-paste-ready implementations for every project file (app, routes, model, all three middleware, service, serializer, migration, Rakefile), and a concrete command list including `bundle exec rake db:migrate` and `curl http://localhost:4567/api/health`. This matches anchor 5 — fully executable, copy-paste ready, covering the common cases.

Workflow Clarity

"First Steps After Scaffold" gives a clear 6-step sequence with an explicit verification checkpoint (step 6: curl the health endpoint), and the scaffold command itself is sequenced (init → bundle → directories). It falls short of anchor 5 because there is no error-recovery guidance — e.g. what to do when `rake db:create`/`db:migrate` fails due to a wrong `DATABASE_URL` or missing PostgreSQL.

Progressive Disclosure

No bundle files exist at all, and roughly 400 lines of complete file templates (middleware, routes, serializer, Rakefile, migration) are inlined in SKILL.md. Section headers are clear and navigation is easy, so it is above anchor 2's "minimal structure", but content that would classically live in a `references/` or `templates/` bundle is inline with no external split, matching anchor 3.

Specificity

"Scaffold a production-ready Sinatra 4.x API with Ruby 3.3+" names a concrete action, and the enumeration "modular application style, Rack middleware, Sequel for database access, Puma web server, and structured project layout" lists several specific stack components with only minor coverage gaps (no mention of testing or auth scaffolding). It is below anchor 5 because there is only one action verb (scaffold) rather than multiple distinct actions.

Completeness

The "what" is clear (scaffold a Sinatra 4.x API with the listed stack), but there is no "Use when…" clause or any equivalent explicit trigger guidance, so completeness is capped at 3 per the judging guidelines. The "when" is only weakly implied by the stack listing.

Trigger Term Quality

Natural terms users would say are present — "Sinatra", "Ruby 3.3+", "API", "Puma", "Sequel", "Rack" — giving good keyword coverage. It falls short of anchor 5 because common variations and synonyms are missing, e.g. "Sinatra app", "Ruby web app", "Ruby backend", or "new Ruby project".

Distinctiveness Conflict Risk

"Sinatra 4.x", "Sequel", "Puma web server", and "Rack middleware" carve out a clear niche that is distinct from Rails starters or generic Ruby project skills, with minimal conflict risk. It is above anchor 4 because the stack terms are specific enough that a user asking for Rails or a non-Ruby backend would not naturally trigger this skill.