Walks the Anthropic Skill best-practices checklist plus the RCS Layer-3 documentation contract for authoring a new skill. Covers gerund-form naming, third-person frontmatter description, the 11 required H2 sections in order, the ≤ 500-line body cap with reference/ bundles, one-level-deep reference linking, and the eval-first discipline (3 scenarios written before the body). Use when the user wants to write a new skill — for any host (Claude Code, Copilot CLI, Gemini CLI, Anthropic API plugin) — and needs the authoring rules plus a skeleton to fill in.
