Claude Code Skills overview

Claude Code Skills as a cross-cutting topic - the plugin-distributed slash-command units that extend an agent session with packaged domain-specific behaviors. Covers skill YAML/Markdown authoring, argument substitution patterns ($ARGUMENTS, $N, named variables), trigger conditions and discovery metadata, skill-to-skill composition, user-level vs project-level vs plugin-bundled skill scopes, and the marketplace distribution model through .claude-plugin packages.