How to Build Reusable AI Agent Skills with Anthropic’s Skill Creator

What is a Skill?

A Skill is a reusable work unit for AI agents, not merely a prompt. It should contain at least four layers: goal definition, structure constraints, judgment rules, and product boundaries.

skill-name/
├── SKILL.md        # Core description (required)
├── scripts/         # Executable scripts
├── references/      # Documentation or knowledge
├── assets/          # Additional resources

The SKILL.md file is the most important component; it must include a clear description, metadata, and concrete instructions.

Goal definition: what problem the skill solves.

Structure constraints: which dimensions the output must cover.

Judgment rules: how to handle insufficient information and mark uncertainties.

Product boundaries: the deliverable must be consumable by downstream processes.

If the first two layers are missing, the skill is unstable; if the last two are missing, it cannot enter a workflow.

Using Skill Creator

GitHub address: https://github.com/anthropics/skills/tree/main/skills/skill-creator

Skill Creator is an official Anthropic tool that helps developers quickly create, optimize, and package skills. Install it once and avoid installing unnecessary skills to save token usage.

01 Quick Installation

npx skills add https://github.com/anthropics/skills --skill skill-creator

02 Workflow

The workflow follows a closed‑loop development, comparative testing, and quantitative evaluation approach:

Capture Intent & Plan : clarify user intent and trigger scenario.

Write Draft : create a SKILL.md with metadata and specific instructions.

Test & Run : run side‑by‑side tests with and without the skill.

Evaluate & Analyze : draft objective assertions, collect performance data, and generate benchmark reports.

Iterate & Refine : analyze feedback, fix defects, and improve instructions until satisfied.

Description Optimization (optional) : fine‑tune the description to improve trigger precision.

03 Quick Use

In Claude Code use /skill-creator; in Codex use $skill-creator and then provide your natural‑language requirements. The CLI will ask clarifying questions to help shape the skill.

Building Your Own Skills

Effective skills are built through a five‑step iterative process rather than a one‑off prompt:

Write a template first, not the skill itself. Organize recurring structures into a Markdown template and define required outputs.

Overlay context and domain‑specific rules onto the template to generate an initial draft.

Polish the draft without immediately solidifying it; focus on identifying systematic errors and missing elements.

Feed the satisfactory result back into the template, improving it for future reuse.

When the template is stable and the rules are clear, use Skill Creator to encapsulate it into a final Skill.

This continuous convergence turns verified work methods into reusable assets that can be quickly applied to new projects.

Appendix

A demo using a DDD modeling skill illustrates the workflow with screenshots.

Reference: https://agentskills.io/what-are-skills

Reference: https://skillsmp.com/zh/skills/anthropics-skills-skills-skill-creator-skill-md