Conciseness

The body is lean and table-driven with no explanation of concepts Claude already knows — every section (typography, conversions, checklist, source paths) carries skill-specific information only. It matches anchor 5 (lean, every token earns its place); not anchor 4 since there is no over-explanation to trim.

Actionability

Concrete, copy-paste-ready guidance throughout: exact character mappings ("`—` (U+2014)" vs "`---`"), exact format-conversion pairs ("`[key]{.smallcaps}`" → "`<kbd>Key</kbd>`"), a before/after code-block example, a specific build command ("npm run build"), and absolute source paths. This covers the common cases as anchor 5 requires; the few genuinely ambiguous rows (page-reference linking) are appropriately delegated to the reference files.

Workflow Clarity

A validation checkpoint is explicitly present ("Validation Checklist — Before committing migrated content" with checkboxes and "Build passes (`npm run build`)"), so the batch-operation cap of 3 does not apply. However, the step-by-step sequence itself is not in the body — it is delegated to references/workflow.md — so it fits anchor 4 (checkpoints present, minor gaps) rather than anchor 5's fully explicit sequenced workflow with feedback loops in the body.

Progressive Disclosure

Clear overview structure: quick-reference tables inline, with three well-signaled one-level-deep references ("[Typography Rules](./references/typography.md)", "[Formatting Guide](./references/formatting.md)", "[Workflow Checklist](./references/workflow.md)"), all of which exist in the bundle. This matches anchor 5; not anchor 4 since navigation and content split are clean with no organization gaps.

Specificity

The description names the domain and two concrete actions — "migrating book content to website, converting chapter formatting" — but "making any changes to migrated content" is a vague catch-all and there is no mention of the actual conversion work (typography, admonitions, code blocks, figures). It matches anchor 3 (1-2 concrete actions, not comprehensive) better than anchor 4, which expects several specific actions with only minor gaps.

Completeness

It explicitly answers what ("migrating book content to website, converting chapter formatting") and when, with a concrete trigger clause: "Use when the user mentions 'migration', 'book content', 'chapter', or edits files in docs/...". This mirrors the anchor-5 example pattern; anchor 4 applies only when the 'when' could be more explicit, which is not the case here.

Trigger Term Quality

Triggers like "migration", "book content", "chapter", and "edits files in docs/ that correspond to book chapters" are natural phrases a user would say. A few natural variants are missing (e.g., "convert chapters", "book-to-website", "manuscript"), so it fits anchor 4 (good coverage, a few terms missing) rather than anchor 5's comprehensive synonym/extension coverage.

Distinctiveness Conflict Risk

The niche (book-to-website chapter migration) is mostly distinct, grounded by terms like "book content" and "chapter". However, the bare trigger "migration" unqualified could also fire on database or code-migration requests, giving minor overlap risk — anchor 4 rather than anchor 5's minimal-conflict clear niche.