<essential_principles> Skills are modular, filesystem-based capabilities that provide domain expertise on demand. They follow the Agent Skills open standard. Custom slash commands (.claude/commands/) have been merged into skills — existing commands keep working, but skills add directory support, frontmatter options, and auto-discovery.

1. Skills Are Prompts — All prompting best practices apply. Be clear, be direct, use XML structure. Assume Claude is smart — only add context Claude doesn't have.

2. SKILL.md Is Always Loaded — When a skill is invoked, Claude reads SKILL.md. Use this guarantee:

Essential principles go in SKILL.md (can't be skipped)
Workflow-specific content goes in workflows/
Reusable knowledge goes in references/

3. Router Pattern for Complex Skills:

skill-name/
├── SKILL.md              # Router + principles
├── workflows/            # Step-by-step procedures (FOLLOW)
├── references/           # Domain knowledge (READ)
├── templates/            # Output structures (COPY + FILL)
└── scripts/              # Reusable code (EXECUTE)

manage-skills