skill-creator
Skill Creator
Skill Creator is Anthropic's open-source agent skill for making skills: the agent drafts a SKILL.md with you, tests it with and without the skill, and tunes its description so it triggers.
Install Skill Creator
In Claude Code, add Anthropic's skills marketplace
/plugin marketplace add anthropics/skillsThen install the example-skills plugin, which holds this skill and Anthropic's other example skills
/plugin install example-skills@anthropic-agent-skillsOr install only this skill, for any agent, with the skills CLI
npx skills add anthropics/skills --skill skill-creatorIn Claude.ai, Anthropic says its example skills are already available on paid plans: switch them on under Customize > Skills.
Or paste this into your coding agent: Install the agent skill skill-creator from github.com/anthropics/skills.
A skill can include scripts that run on your computer, so read its source first.
What Skill Creator does
Skill Creator is Anthropic's skill for writing new skills and improving existing ones. It loads when you want to create a skill from scratch, edit one, test it with evals, benchmark it or improve how reliably its description triggers. The agent works out where you are in the process: it can capture a workflow from the current conversation, interview you about edge cases and formats, then write the SKILL.md.
For testing with Skill Creator, the agent writes two or three realistic prompts and runs each one with the skill and without it (or against the old version), using sub-agents in parallel. It grades the outputs against checks, aggregates pass rate, time and tokens into a benchmark, and opens a bundled review page where you read each output and leave feedback. It then revises the skill from your feedback and runs the tests again.
A separate Skill Creator loop tunes the description: 20 queries that should and should not trigger the skill, split into training and held-out sets, each run three times, for up to five rounds of rewrites. That loop needs the claude command-line tool, so it runs in Claude Code and is skipped in Claude.ai, where tests also run one at a time. A script packages the result as a .skill file.
When to use Skill Creator
- You keep giving your agent the same instructions and want to turn them into a skill.
- You wrote a skill and want to know whether it actually improves the results.
- Your skill does not load when it should, and you want its description tuned.
- You want to package a skill as a file you can install or share.
When to pick something else
- You want a strict test-first method that closes loopholes in discipline skills: Writing Skills from Superpowers.
Which agents Skill Creator works in
Anthropic documents Skill Creator for Claude Code, Claude.ai, Claude API. The open skills CLI also installs it into 78 agents, including Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot, OpenCode (we listed it with the CLI on October 1, 2026). See where each agent looks for skills.
Parallel test runs, baselines and blind comparison need subagents, which Claude Code and Cowork have; in Claude.ai tests run one at a time and benchmarking is skipped. Description tuning calls claude -p, so it needs the Claude Code command-line tool.
Skill Creator license
Skill Creator is published under Apache-2.0. Apache-2.0 comes from the LICENSE.txt in the skill folder (read 2026-10-01); the SKILL.md itself has no license key and the anthropics/skills repository has no root license file. In practice you may use, change and share it in any agent if you keep the license text and notices and mark your changes.
Questions people ask
Does skill-creator work outside Claude Code?
Partly. Drafting a SKILL.md and packaging it work in any agent with Python and a filesystem. Parallel test runs need subagents, and the description tuning loop needs the claude command-line tool (claude -p), which only Claude Code provides.
How is skill-creator different from Superpowers' writing-skills?
Skill Creator measures a skill: runs with and without it, graded benchmarks, a review page and description tuning. Writing Skills applies test-driven development: pressure scenarios with subagents before and after the skill exists, aimed at closing loopholes.
Related skills for building skills and mcp servers
- Writing Skills: Writing Skills is an agent skill from Superpowers: your agent writes new skills test-first, running pressure scenarios with subagents before and after the skill exists.
- MCP Builder: MCP Builder is Anthropic's open-source agent skill for building MCP servers in TypeScript or Python, from API research and tool design to testing and a 10-question evaluation.
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