Conciseness

The ~13-line body is lean and dense: Trigger, Fix, and Why each carry only non-obvious, repo-specific information ("a field line, an enum line, or a convert or schema branch"; "customthing covers custom methods, root and nested requestValue..."). Nothing explains concepts Claude already knows, so every token earns its place — a direct match for the level-5 anchor, and clearly above level 4 where trimming would still be possible.

Actionability

The guidance is fully executable: a copy-paste command ("go test ./internal/generator -run TestGoldenOutput<Name> -update"), a specific fixture directory ("internal/generator/testdata"), and a named model fixture ("customthing") that covers the common cases (requestValue, readNullAs, readEmptyAs, requireOne, readRejected, unwrap, default-missing enum). This matches the level-5 anchor — executable commands plus a concrete example covering common cases — with nothing reduced to pseudocode.

Workflow Clarity

The sequence is clear and unambiguous — add/extend the fixture, run the test with -update, commit the golden — and it ends with an explicit validation checkpoint ("A second run without -update must pass"). This is a simple single-purpose skill under 50 lines whose action is unambiguous, and validation is explicitly present, so the level-5 anchor applies; level 4 would require missing checkpoints, which is not the case.

Progressive Disclosure

The skill is under 50 lines, has no need for external references (none exist in the bundle), and is organized into clear, well-signaled sections (Trigger / Fix / Why). Per the rubric's guidance for short reference-free skills, this matches the level-5 anchor; there is no inlined content that belongs in a separate file.

Specificity

The description names its domain precisely ("adding a generator key or branch in tools/iac-codegen") and gives one concrete action ("Cover it with a golden fixture"), matching the anchor for 1-2 concrete actions. It does not list several distinct actions, so it falls below the level-4 anchor; and because it names both the domain and a concrete action, it is above the level-2 anchor where actions are minimal or generic.

Completeness

Both questions are answered explicitly with concrete trigger phrases: "Use when adding a generator key or branch in tools/iac-codegen" states when, and "Cover it with a golden fixture" states what, plus an explicit exclusion ("Do NOT use for a resource-only override line"). This matches the level-5 anchor exactly; level 4 would require a weaker or less explicit 'when', which is not the case here.

Trigger Term Quality

Natural codebase terms are well covered: "generator key", "branch", "tools/iac-codegen", "golden fixture", and "resource-only override line" — phrases a developer on this repo would actually say. A few natural synonyms are missing (e.g., "golden test", "snapshot test", "testdata"), so it does not reach the comprehensive level-5 anchor; it clearly exceeds level 3, where common variations are absent.

Distinctiveness Conflict Risk

The niche is highly distinct (golden fixtures for generator keys in one specific tool path) and even includes an explicit negative trigger ("Do NOT use for a resource-only override line") to prevent misfires. Conflict risk is minimal, matching the level-5 anchor; no neighboring anchor fits better.