The Claude Code Skill ecosystem is exploding with growth, reaching over 87,000 GitHub stars as developers rush to create custom workflows. Skills let you teach Claude specific tasks through structured instructions, using progressive disclosure to keep context windows manageable. Metadata triggers loading, while detailed instructions and resources load on demand.

Before building, understand when Skills make sense versus MCP servers or Subagents. Skills teach behavior like analysis workflows or coding standards. MCP servers provide new tools like database queries. Subagents run independent work in separate contexts. The kitchen analogy helps: MCP is your equipment, Skills are your recipes. You can combine them—Sentry's code review Skill uses MCP for error data—but many workflows need only Skills.

Start with concrete use cases before writing code. Define who uses it, their exact requests, inputs, and expected outputs. For an e-commerce review Skill, that meant analyzing CSV order data to generate KPI breakdowns and action plans. Write a specific YAML frontmatter with trigger keywords like 'sales data' or 'revenue analysis.' Then choose your pattern: prompt-only for simple rules, or prompt plus scripts for complex processing. Keep SKILL.md under 500 lines, moving detailed content to references/ when needed.