Skill Master Skill | Agent Skills

Skill Master

Create, edit, and validate Agent Skills following the open agentskills.io specification. This skill is the entry point for creating and maintaining Agent Skills.

Language requirement: all skills MUST be authored in English.

Quick Navigation

New to skills? Read: references/specification.md
SKILL.md templates? See: assets/skill-templates.md
Writing effective descriptions & instructions? Read: references/writing-skills.md
Structuring multi-step processes? Read: references/workflows.md
Adding scripts to a skill? Read: references/scripts.md
Adding assets/templates to a skill? Read: references/assets.md
Advanced features (context, agents, hooks)? Read: references/advanced-features.md
Creating from docs? Read: references/docs-ingestion.md
Testing & troubleshooting? Read: references/testing-troubleshooting.md
Validation & packaging? See scripts/

When to Use

Creating a new skill from scratch
Updating an existing skill
Creating a skill by ingesting external documentation
Validating or packaging a skill for distribution

Skill Structure (Required)

my-skill/
├── SKILL.md          # Required: instructions + metadata (must be human-readable too)
├── metadata.json     # Optional: extended metadata for publishing
├── references/       # Optional: documentation, guides, API references
├── examples/         # Optional: sample outputs, usage examples
├── scripts/          # Optional: executable code
└── assets/           # Optional: templates, images, data files

Note on README.md: Anthropic's official guide strictly prohibits including a README.md inside the skill folder to avoid confusing the agent. SKILL.md is the single source of truth and must be written to be equally readable by humans and agents. If you are migrating an existing skill that has a README.md, merge its useful information (like links and brief description) into SKILL.md and delete the README.md.

Folder Purposes (CRITICAL)

| Folder | Purpose | Examples | | ------------- | ------------------------------------------ | ------------------------------------------------------- | | references/ | Documentation for agents to read | Guides, API docs, concept explanations, troubleshooting | | examples/ | Sample outputs showing expected format | Output examples, usage demonstrations | | assets/ | Static resources to copy/use | Document templates, config templates, images, schemas | | scripts/ | Executable code to run | Python scripts, shell scripts, validators |

When to Use Each

Use references/ for:

Detailed documentation about concepts
API references and usage guides
Troubleshooting and FAQ
Anything the agent needs to read and understand

Use examples/ for:

Sample outputs showing expected format
Usage demonstrations
Before/after comparisons
Anything showing what the result should look like

Use assets/ for:

Document templates (markdown files to copy as starting point)
Configuration file templates
Schema files, lookup tables
Images and diagrams
Anything the agent needs to copy or reference verbatim

IMPORTANT: Templates belong in assets/, examples in examples/, documentation in references/.

Frontmatter Schema

Every SKILL.md MUST start with YAML frontmatter:

---
name: skill-name
description: "What it does. Keywords: term1, term2."
version: "1.2.3"
release_date: "2026-01-01"
metadata:
  author: your-name
---

Field order: name → description → version → release_date → license → compatibility → metadata

Required Fields

| Field | Constraints | | ----------- | ------------------------------------------------------------------------------------------- | | name | 1-64 chars, lowercase a-z0-9-, no --, no leading/trailing -, must match folder name | | description | 1-1024 chars (target: 80-150), describes what skill does + when to use it, include keywords |

Optional Fields (Top Level)

| Field | Purpose | | ------------- | ------------------------------------------------------------ | | version | Upstream product version; "—" if product has no versioning | | release_date | Date skill was last meaningfully updated (YYYY-MM-DD) | | license | License name or reference to bundled LICENSE file | | compatibility | Environment requirements (max 500 chars) | | metadata | Object for arbitrary key-value pairs (see below) |

metadata Object (Common Fields)

| Field | Purpose | | ------------- | --------------------------------------------- | | author | Author name or organization | | argument-hint | Hint for autocomplete, e.g., [issue-number] |

Optional Fields (Claude Code / Advanced)

| Field | Purpose | | ------------------------ | -------------------------------------------------------------------------- | | disable-model-invocation | true = only user can invoke (via /name). Default: false | | user-invocable | false = hidden from / menu, only agent can load. Default: true | | allowed-tools | Space-delimited tools agent can use without asking, e.g., Read Grep Glob | | model | Specific model to use when skill is active | | context | Set to fork to run in a forked subagent context | | agent | Subagent type when context: fork, e.g., Explore, Plan | | hooks | Hooks scoped to skill's lifecycle (see agent documentation) |

Invocation Control Matrix

| Frontmatter | User can invoke | Agent can invoke | Notes | | -------------------------------- | --------------- | ---------------- | --------------------------------------- | | (default) | ✅ Yes | ✅ Yes | Description in context, loads when used | | disable-model-invocation: true | ✅ Yes | ❌ No | For manual workflows with side effects | | user-invocable: false | ❌ No | ✅ Yes | Background knowledge, not a command |

Variable Substitutions

Available placeholders in skill content:

| Variable | Description | | ---------------------- | -------------------------------------------------------- | | $ARGUMENTS | All arguments passed when invoking the skill | | ${CLAUDE_SESSION_ID} | Current session ID for logging or session-specific files |

If $ARGUMENTS is not in content, arguments are appended as ARGUMENTS: <value>.

Example:

---
name: fix-issue
description: Fix a GitHub issue
disable-model-invocation: true
---
Fix GitHub issue $ARGUMENTS following our coding standards.

Dynamic Context Injection

Use !command`` syntax to run shell commands before skill content is sent to the agent:

## Pull request context

- PR diff: !`gh pr diff`
- Changed files: !`gh pr diff --name-only`

## Your task

Review this pull request...

The command output replaces the placeholder, so the agent receives actual data.

metadata.json (Optional)

For publishing or extended metadata, create metadata.json:

{
  "version": "1.0.0",
  "organization": "Your Org",
  "date": "January 2026",
  "abstract": "Brief description of what this skill provides...",
  "references": ["https://docs.example.com", "https://github.com/org/repo"]
}

Fields:

version — Skill version (semver)
organization — Author or organization
date — Publication date
abstract — Extended description (can be longer than frontmatter)
references — List of source documentation URLs

Name Validation Examples

# Valid
name: pdf-processing
name: data-analysis
name: code-review

# Invalid
name: PDF-Processing  # uppercase not allowed
name: -pdf            # cannot start with hyphen
name: pdf--processing # consecutive hyphens not allowed

Description Rules

Purpose: Tell the LLM what the skill does and when to activate it. Minimize tokens — just enough for activation decision.

Formulas:

For library/reference skills (Claude Code, keyword-based discovery):

[Product] [core function]. Covers [2-3 key topics]. Keywords: [terms].

For workflow/automation skills (Claude.ai, trigger-based activation):

[What it does]. Use when user [specific trigger phrases].

Critical for auto-triggering: include explicit "Use when user says / asks / mentions..." phrases. Without them, Claude may not load the skill automatically. See references/writing-skills.md for good/bad examples and debugging tips.

Constraints:

Target: 80-150 chars
Max: 1024 chars (300 if keeping it minimal)
No marketing ("powerful", "comprehensive", "modern")
No filler ("this skill", "use this for", "helps with")
No XML angle brackets < >
Names with "claude" or "anthropic" are reserved

Good examples:

description: "Turso SQLite database. Covers encryption, sync, agent patterns. Keywords: Turso, libSQL, SQLite."

description: "Base UI unstyled React components. Covers forms, menus, overlays. Keywords: @base-ui/react, render props."

description: "Inworld TTS API. Covers voice cloning, audio markups, timestamps. Keywords: Inworld, TTS, visemes."

Poor examples:

# Too vague
description: "Helps with PDFs."

# Too verbose
description: "Turso embedded SQLite database for modern apps and AI agents. Covers encryption, authorization, sync, partial sync, and agent database patterns."

# Marketing
description: "A powerful solution for all your database needs."

Keywords: product name, package name, 3-5 terms max.

How Skills Work (Progressive Disclosure)

Discovery: Agent loads only name + description of each skill (~50-100 tokens)
Activation: When task matches, agent reads full SKILL.md into context
Execution: Agent follows instructions, loads referenced files as needed

Key rule: Keep SKILL.md under 500 lines. Move details to references/.

Creating a New Skill

Pro Tip: You can use the skill-creator skill (available in Claude.ai or Claude Code) to interactively generate your first draft, then refine it using the steps below.

Step 1: Scaffold

python scripts/init_skill.py <skill-name>
# Or specify custom directory:
python scripts/init_skill.py <skill-name> --skills-dir skills

Or manually create:

<skills-folder>/<skill-name>/
├── SKILL.md
├── references/   # For documentation, guides
└── assets/       # For templates, static files

Step 2: Write Frontmatter

---
name: <skill-name>
description: "[Purpose] + [Triggers/Keywords]"
---

Step 3: Write Body

Recommended sections:

When to use (triggers, situations)
Quick navigation (router to references and assets)
Steps / Recipes / Checklists
Critical prohibitions
Links

Step 4: Add References (documentation)

For each major topic, create references/<topic>.md with:

Actionable takeaways (5-15 bullets)
Gotchas / prohibitions
Practical examples

Step 5: Add Scripts (if applicable)

Consult references/scripts.md for when scripts are worth writing and how to structure them.

Language selection:

Python — default for CLI wrappers, validators, scaffolding
Go — when the skill's ecosystem is Kubernetes/cloud-native (see k8s-cluster-api)
JS/TS — when the skill's ecosystem is Node/npm

Minimal checklist for a script:

argparse (Python) or flag (Go) for all parameters — no hardcoded values
Check tool availability before use (shutil.which() in Python)
Docstring at top with Usage + Examples
All exceptions caught; exit non-zero with a message to stderr

Step 6: Add Assets (if needed)

Consult references/assets.md for when assets are worth creating and how to format them.

For templates or static resources, create assets/<resource>. Common types:

Config templates — .minimal.yaml / .full.yaml pair; add # yaml-language-server: $schema= header
YAML manifests — use ${VAR_NAME:=default} for variables; include purpose + usage comment at top
Text templates — use #-prefixed comments to explain fields and valid values
Markdown checklists / runbooks — - [ ] checkboxes, inline commands, sign-off section
Prompt / prose templates — grouped by use case, each block self-contained

Naming: <tool>.minimal.yaml, <purpose>-checklist.md, <name>.template, <topic>-prompts.md.

Step 7: Validate

python scripts/quick_validate_skill.py <skill-path>

Creating a Skill from Documentation

When building a skill from external docs, use the autonomous ingestion workflow:

Phase 1: Scaffold

Create skill folder with SKILL.md skeleton
Create plan.md for progress tracking
Create references/ directory

Phase 2: Build Queue

For each doc link:

Fetch the page
Extract internal doc links (avoid nav duplicates)
Prioritize: concepts → API → operations → troubleshooting

Phase 3: Ingest Loop

For each page:

Fetch one page
Create references/<topic>.md with actionable summary
Update plan.md checkbox
Update SKILL.md if it adds a useful recipe/rule

Do not ask user after each page — continue autonomously.

Phase 4: Finalize

Review SKILL.md for completeness
Ensure practical recipes, not docs mirror
plan.md may be deleted manually after ingestion

Critical Prohibitions

Do NOT copy large verbatim chunks from vendor docs (summarize in own words)
Do NOT write skills in languages other than English
Do NOT include project-specific secrets, paths, or assumptions
Do NOT keep SKILL.md over 500 lines
Do NOT skip name validation (must match folder name)
Do NOT use poor descriptions that lack trigger keywords
Do NOT omit product version when creating skills from documentation

Version Tracking

What `version` Means

version holds the upstream product version the skill was built against (e.g., "1.12.3" for CAPI v1.12.3). For standalone skills not tied to an external product, it holds the skill's own version (e.g., "1.2.4" for skill-master).

Use "—" when the product uses continuous deployment with no semantic versioning (e.g., hosted services like Cloudflare Workers).

When to Update

| Trigger | Update version | Update release_date | | ------------------------------------ | ---------------- | --------------------- | | Product released a new version | ✅ Yes | ✅ Yes | | Content changed, no upstream version | ❌ No | ✅ Yes | | Typo or minor fix | ❌ No | ❌ No |

When bumping version or making significant content changes, also update:

SKILLS_VERSIONS.md — set new version + date, move row to top of table
CHANGELOG.md — prepend a new dated block at the top

Creating a Skill from Docs

Set version to the exact upstream version you documented (check the release page)
Set release_date to today's date
Ensure SKILL.md has an overview (1-2 sentences) + ## Links section

Links format:

## Links

- [Documentation](https://example.com/docs)
- [Changelog](https://example.com/changelog)
- [GitHub](https://github.com/org/repo)
- [npm](https://www.npmjs.com/package/name)

Order: Documentation → Changelog/Releases → GitHub → Package registry. Include only applicable links.

Validation Checklist

Pro Tip: You can use the skill-creator skill (available in Claude.ai or Claude Code) to review your skill and suggest improvements before finalizing.

[ ] name matches folder name, kebab-case, 1-64 chars, no --
[ ] description includes WHAT it does AND WHEN to use it (trigger phrases)
[ ] description has no XML angle brackets < >
[ ] SKILL.md under 500 lines
[ ] Documentation in references/, templates in assets/
[ ] Complex multi-step processes extracted to references/workflows.md
[ ] All text in English
[ ] Skill triggers on obvious test queries
[ ] Skill does NOT trigger on unrelated queries

Full pre-publish checklist: references/testing-troubleshooting.md

Scripts

| Script | Purpose | | ------------------------- | ------------------------------------------------------- | | init_skill.py | Scaffold new Agent Skill (agentskills.io) | | init_copilot_asset.py | Scaffold Copilot-specific assets (instructions, agents) | | quick_validate_skill.py | Validate skill structure | | package_skill.py | Package skill into distributable zip |

Agent Skills: Skill Master

Install this agent skill to your local

Skill Files