Conciseness

The body is efficient and assumes competence — no explaining what YAML or Python is, and concrete cost framing ('a 300-line file's header costs ~50 tokens'). Minor trimming possible: the '## Why this works' section is motivational rather than instructional, and the four per-language wrapper examples duplicate detail the body itself says `generate` produces automatically and `SPECIFICATION.md` fully documents. Matches the 4 anchor (efficient, minor over-explanation) rather than the 5 anchor (every token earns its place).

Actionability

Fully executable guidance throughout: exact commands with flags ('python scripts/frontmatter.py index <dir> [--format md|json] [--min-lines N]', 'generate <file> [--write]', 'validate <dir>' with exit-1 note), a copy-paste-ready parameterized Grep call, `Read` with `limit: 20`, a worked purpose example ('Genetic algorithm for FPL squad optimisation' beats 'GA module'), and a field table with formats. Matches the 5 anchor.

Workflow Clarity

Both modes are clearly sequenced as numbered steps with an explicit validation checkpoint — 'Validate before you finish. Run validate <dir>; fix any unresolved `related` paths or empty purposes' — that enumerates the failure modes, plus a no-frontmatter fallback ('No frontmatter? Say so and fall back'). Matches the 5 anchor (explicit validation steps and error-recovery guidance); the 4 anchor would require missing checkpoints, which are present in both workflows.

Progressive Disclosure

Good structure: the main file is self-sufficient for the common case and explicitly defers the full schema ('Don't read the example files or `SPECIFICATION.md` unless you need the full schema'; 'See `SPECIFICATION.md` for the complete per-language reference'), and `scripts/frontmatter.py` exists with exactly the documented index/generate/validate subcommands. However, `SPECIFICATION.md` and the 'example files' are referenced but absent from the bundle — dangling references are a minor organization gap, matching the 4 anchor rather than 5.

Specificity

Multiple concrete actions are stated — 'Index a tree's headers in one pass', 'generate or validate frontmatter with the bundled scripts', 'add/maintain file-level documentation' — covering navigation, authoring, and validation comprehensively. This matches the 5 anchor (multiple specific concrete actions, comprehensive coverage); the 4 anchor would require a noticeable coverage gap, and none exists.

Completeness

Both what ('Context-efficient codebase navigation and documentation using structured frontmatter headers… Index a tree's headers in one pass… generate or validate frontmatter with the bundled scripts') and when ('Use this when exploring an unfamiliar codebase, answering "where is X / how does Y work" questions, or when asked to add/maintain file-level documentation') are explicit with concrete trigger phrases, exactly matching the 5 anchor.

Trigger Term Quality

Natural phrases users would actually say are present: 'exploring an unfamiliar codebase', 'where is X / how does Y work', 'add/maintain file-level documentation', 'token budget matters while navigating code'. Falls short of the 5 anchor (comprehensive synonyms) because common variants like 'codebase overview', 'onboarding', or 'understand the code' are absent.

Distinctiveness Conflict Risk

The frontmatter-header niche is distinct and the description scopes triggers to it, but 'exploring an unfamiliar codebase' and 'token budget matters while navigating code' are broad enough to overlap with general code-exploration/search skills — the 4 anchor (mostly distinct, minor overlap risk with closely related skills) fits better than 5.