Conciseness

Every section — auth, endpoint, parameters, response shape, worked example, content safety, errors, routing, references — carries information Claude cannot infer, and none teaches known concepts. The one non-operational section (content safety) is three sentences and earns its place, matching the "lean and efficient; every token earns its place" anchor.

Actionability

The body gives the exact endpoint, the exact auth header with format, a copy-paste curl example with jq projection, a full response schema, and a parameter table. This is fully executable and covers the common case, matching the top anchor.

Workflow Clarity

This is a simple, single-purpose skill (one authenticated GET), and the single action is unambiguous: a worked example plus explicit error handling (401 missing key, 429 retry with backoff) provides the feedback loop. Per the simple-skill guidance this earns the top score; there are no destructive or batch operations to trigger a cap.

Progressive Disclosure

The body is short with well-organized sections, and detail lives one level deep in clearly signaled external references (OpenAPI operation ListEarthquakes, auth matrix). There are no bundle files to misplace content, and navigation is trivial — matching the well-organized-sections exception for compact skills.

Specificity

"Retrieve recent earthquakes (USGS) with magnitude, depth, location, and a concern score that flags proximity to nuclear test sites" lists multiple concrete actions with comprehensive coverage of what is returned. It goes beyond naming the domain — every data element is enumerated — so it matches the top anchor rather than 4, where minor coverage gaps would be expected.

Completeness

The description answers both questions explicitly: what ("Retrieve recent earthquakes (USGS) with magnitude, depth, location, and a concern score...") and when ("Use when the user asks about recent seismic activity or whether an earthquake was natural"), with concrete trigger phrases — a direct match to the top anchor.

Trigger Term Quality

"Use when the user asks about recent seismic activity or whether an earthquake was natural" supplies natural phrases users would say, but coverage stops short of the comprehensive-with-synonyms level of the 5 anchor. Missing common variations such as "quake", "tremor", "aftershock", or "epicenter".

Distinctiveness Conflict Risk

The niche is narrow and distinctive — seismology data plus nuclear-test-site concern scoring — with trigger terms ("recent earthquakes", "seismic activity", "was an earthquake natural") that would not plausibly fire sibling hazard skills. Clear niche with distinct triggers and minimal conflict risk.