# Compound Skill

> Use when creating a compound skill — a structured knowledge base for a project or topic that uses a SKILL.md routing table and reference documents. Covers the research phase, topic decomposition, SKILL.md frontmatter and routing table format, reference document structure, cross-referencing, and maintenance. Triggers on: "compound skill", "create skill", "write skill", "skill template", "skill structure", "routing table", "reference document", "skill authoring", "skill creation guide".

- Skill: `carapace-sh/compound-skill` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add carapace-sh/compound-skill`
- Raw SKILL.md: https://api.skillmd.com/api/skills/carapace-sh/compound-skill/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Research & Search
- Author: carapace-sh (https://skillmd.com/u/carapace-sh)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/carapace-sh/compound-skill

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# Creating a Compound Skill

Guide for creating a compound skill — a structured knowledge base that provides in-depth reference documentation for a project, technology, or topic. A compound skill consists of a **SKILL.md** routing table and a set of **reference documents** in a `references/` directory.

## Sub-Resources

Load the reference that matches your task. When in doubt, load multiple references.

| Keywords | Reference |
|----------|----------|
| research, source code analysis, documentation review, topic decomposition, sub-topic identification, scope boundaries, audience analysis, information sources | [references/research.md](references/research.md) |
| SKILL.md, frontmatter, name, description, triggers, user-invocable, routing table, Sub-Resources table, Quick Guide, Cross-Project References, data flow diagram | [references/skill-md.md](references/skill-md.md) |
| reference document, structure, heading, code example, table, cross-reference, source attribution, depth level, naming convention | [references/reference-doc.md](references/reference-doc.md) |
| cross-reference, link, overlap avoidance, delegation, Cross-Project References, stay on topic, DRY, complementary scope | [references/cross-referencing.md](references/cross-referencing.md) |
| maintenance, update triggers, adding references, removing references, keeping current, version skew, changelog | [references/maintenance.md](references/maintenance.md) |

## Quick Guide

- **How do I start creating a compound skill?** → [references/research.md](references/research.md)
- **How do I write the SKILL.md routing table?** → [references/skill-md.md](references/skill-md.md)
- **How do I structure a reference document?** → [references/reference-doc.md](references/reference-doc.md)
- **How do I handle cross-references without duplicating?** → [references/cross-referencing.md](references/cross-referencing.md)
- **How do I keep a skill up to date?** → [references/maintenance.md](references/maintenance.md)
- **What goes in the frontmatter description?** → [references/skill-md.md](references/skill-md.md)
- **How do I decide on sub-topics?** → [references/research.md](references/research.md)
- **How do I name reference files?** → [references/reference-doc.md](references/reference-doc.md)
- **When should I link to another skill instead of writing?** → [references/cross-referencing.md](references/cross-referencing.md)

## Cross-Project References

These existing compound skills serve as real-world examples:

- **carapace-dev** — library development skill with 20+ references (carapace repo, `skills/carapace-dev/`)
- **bash** — shell internals skill with 5 references (carapace repo, `skills/bash/`)
- **jj** — VCS reference skill with 12 references (carapace-jjlex repo, `skills/jj/`)