skill-creator

name: skill-creator description: "Design, create, update, and package Agent Skills following the open AgentSkills specification (agentskills.io). Use when asked to create a new skill, improve an existing skill, scaffold a skill directory, validate a SKILL.md, or package a skill into a distributable .skill file." license: MIT metadata: author: AeonDave version: "1.4"

Skill Creator

Guidance for creating and maintaining high-quality Agent Skills across any AI agent ecosystem.

What Is a Skill

A skill is a self-contained folder that gives an AI agent specialized knowledge, workflows, and tools for a specific domain. Skills use the open AgentSkills specification.

Directory Structure

skill-name/
├── SKILL.md          # Required — frontmatter + instructions
├── scripts/          # Optional — executable code agents can run
├── references/       # Optional — docs loaded on demand into context
└── assets/           # Optional — templates, images, data files used in output

Core Design Principles

1. Brief, Clear, Specific, Useful

The context window is shared. Every token in a skill competes with the user's request. Challenge every sentence: does the agent actually need this to act? Write imperative instructions, not essays. Every skill must directly help the agent act on the task.

2. Progressive Disclosure

Design for staged loading to keep the context clean:

• Discovery: name + description only
• Activation: full SKILL.md body (baseline workflow, routing, and task guidance)
• On demand: explicit triggers load files in scripts/, references/, assets/

If a workflow gets deeply specific, move it to references/ so the agent only loads it when that specific subtask triggers.

3. Agent-Neutral Language

Skills are executed by different AI agents (Claude, Gemini, Codex, etc.). Never hardcode a product name inside the skill body; say "the agent" instead.

4. No Meta-Justification

Keep SKILL.md and references/ files stripped of benchmarks, "why we built this" defenses, and generic README material. Only include actionable rules and necessary constraints. Tell the agent what to do and the operational why (e.g., "because command X hangs the service"), not the philosophical why.

Skill Creation Process

Follow these steps to build or refactor a skill:

Step 1: Understand or Audit

Gather concrete usage examples first.

• New skill: Ask what triggers it, what tasks it handles, and what success looks like.
• Update: Read SKILL.md first. Identify what works, what is stale, and what must remain stable.

Step 2: Plan Resources

Ask: what does an agent need to execute this repeatedly?

• scripts/: Use when the same code is rewritten each time or deterministic output is required.
• references/: Use for specific subtasks, schemas, or guides needed dynamically. They must not fill context with non-actionable material.
• assets/: Use for boilerplate or templates the agent copies.

Step 3: Scaffold

For a new skill, run the init script:

python scripts/init_skill.py <skill-name> --path <output-dir> --resources scripts,references,assets --examples

For an existing skill, edit in place. Do not re-scaffold.

Step 4: Author

SKILL.md — Frontmatter

Required fields only:

---
name: my-skill                  # lowercase, hyphens, max 64 chars, matches folder name
description: "Single coherent paragraph covering what it does + when to use it; max 1024 chars."
---

Description rules: The description is the primary routing signal. Explicitly array the trigger words, file types, and scenarios. (Weak: "Helps with PDFs." Strong: "Extract text from PDF files, fill PDF forms. Use when the user asks about PDFs or document extraction.")

SKILL.md — Body

Write step-by-step instructions. Explain intent so agents can generalize, but keep it lean. Always end with a Resources section listing what is in scripts/, references/, and assets/ and exactly when to load them.

References (references/)

• Reference files must extend the skill for a specific subtask.
• Do not use them as a README, training manual, or catalog.
• Add a table of contents at the top of any file over 100 lines.
• Never duplicate content between SKILL.md and a reference file.

What NOT to Include

Do not create: README.md, CHANGELOG.md, INSTALLATION_GUIDE.md. Evict any file that doesn't direct agent behavior.

Step 5: Pressure-Test Behavior

Simulate realistic constraint scenarios (time pressure, authority pressure, sunk cost). Ensure the skill workflow forces the agent to behave correctly (e.g., verifying a scanner finding before claiming it). See references/pressure-testing-skills.md.

Step 6: Validate and Package

# Validate frontmatter
python scripts/quick_validate.py <path/to/skill-folder>

# Package into a .skill archive (validates first)
python scripts/package_skill.py <path/to/skill-folder>

Fix all errors. Resolve all TODO markers.

Step 7: Iterate

After real usage:

• If it under-triggers, improve the description.
• If a section doesn't improve output, remove it.
• If it grows too large, push depth into references/.
• Generalize patches: fix the underlying instruction gap, not just the single failing prompt.

Skill Naming Conventions

• Lowercase letters, digits, and hyphens only (e.g., pdf-extractor).
• Max 64 characters; no leading/trailing/consecutive hyphens.
• Folder name must match the name field exactly.

Reference Files

• See references/patterns.md for progressive disclosure patterns and anti-patterns.
• See references/spec.md for the full AgentSkills frontmatter field reference.
• See references/pressure-testing-skills.md for realistic RED/GREEN behavior tests for skills.
• See references/skill-triggering-tests.md for natural-prompt activation checks.

Scripts