What problem does it solve? Writing a well-structured Claude Skill requires knowing YAML frontmatter rules, description trigger patterns, token limits, eval design, and packaging constraints. This Skill provides a step-by-step guide so new SKILL.md files are correctly structured, trigger reliably, and stay under platform limits. ## Core Features & Use Cases - SKILL.md authoring rules: Enforces mandatory YAML frontmatter (name, description with ALWAYS/DO NOT triggers), the 500-line body limit, and the 1024-character description cap. - Spec-driven TDD workflow: Guides writing a compact spec, deriving evals.json test cases with concrete assertions, and following a RED-GREEN-REFACTOR cycle before creating or updating a skill. - Decision Gate and anti-patterns: Provides an update-vs-create decision table, a catalog of common mistakes, and a pre-packaging checklist including validation and safety gates. - Use Case: When asked to create a new skill for invoice processing, it produces a complete SKILL.md template with Ukrainian-first triggers, 4-6 eval cases, a guard script, and packaging instructions. ## Quick Start Ask the assistant to create a new skill and write its SKILL.md file, and this guide will walk through frontmatter, body structure, evals, and packaging step by step.
