Conciseness

The body is lean and assumes competence — no Terraform or Go basics are explained, and the Renew-semantics and Private-key notes are genuinely non-obvious domain knowledge. It falls short of 5 because the closing Checklist largely restates the Design Rules, Testing, and Documentation sections, adding redundant tokens.

Actionability

The Implementation section is a complete, copy-paste-ready Go example covering Metadata, Schema, Open, Renew, and Close with correct diagnostics handling, plus a full registration snippet. Score 4 would require minor gaps, but the code covers the common case end-to-end and is executable as written (modulo the illustrative client).

Workflow Clarity

The section order (When to Use → Lifecycle → Implementation → Registration → Design Rules → Testing → Documentation → Checklist) forms a clear sequence, with an explicit verification gate (echo-provider tests gated to Terraform >= 1.10) and a closing checklist. It does not reach 5 because there is no error-recovery guidance for when tests or renewal fail.

Progressive Disclosure

Headers are clear and navigation is easy, with no nested references and sensible cross-links to sibling skills. It stays at 4 rather than 5 because the ~100-line implementation listing is inline in SKILL.md where a references/ split would fit, and the sibling-skill pointers are hedged with "(if available)" rather than resolved to concrete paths.

Specificity

The description enumerates multiple concrete actions — "the Open/Renew/Close lifecycle, ephemeral schema design, registration via EphemeralResources, renewal for expiring credentials, and how ephemeral values flow into write-only attributes and provider configuration" — matching the comprehensive multi-action anchor. Score 4 would require minor gaps in coverage, but every core capability of the skill is named.

Completeness

It explicitly answers both questions: the "what" is the implementation capability list, and the "when" is a concrete "Use when adding an ephemeral resource, exposing secrets... deciding between an ephemeral resource and a data source, or wiring short-lived credentials from one provider into another" clause. This mirrors the anchor-5 exemplar structure exactly; a 4 would need the when-clause to be less explicit or concrete.

Trigger Term Quality

Natural phrasing a user would actually say is well covered with synonyms: "adding an ephemeral resource", "exposing secrets/tokens/certificates that must never persist in state or plan", "deciding between an ephemeral resource and a data source", "wiring short-lived credentials". It falls short of the 5 anchor only in omitting a couple of looser variations (e.g. "dynamic credentials", "temporary password"), keeping it at the top anchor rather than above it.

Distinctiveness Conflict Risk

"Terraform provider ephemeral resources" is a narrow, well-defined niche, and the description even pre-empts the nearest collision by naming the "deciding between an ephemeral resource and a data source" case. It is clearly distinguishable from general Terraform provider/data-source skills, so the minimal-conflict anchor applies.