Claude Skill Builder

How to use the skill builder

1. Start from a task you repeat. The best first skill is something you’ve explained to Claude several times: a report format, your email voice, a review checklist, a proposal structure. Click “Load an example” to see a complete skill first.
2. Give it a title. The skill name, which is also the folder name, fills in from the title in the format Claude requires.
3. Write the description carefully. It’s the most important part. Say what the skill does and when to use it, in the words you’d actually type. “Use when the user asks for a follow-up or recap email” helps Claude recognize the moment; “helps with emails” doesn’t.
4. Write the instructions as if for a new employee. Steps, format, voice, length, and what good looks like. Rules and an example are optional but make results much more consistent.
5. Fix anything marked ✗, then download. Items marked ! are recommendations; the download works without them, but the skill will work better with them.

How to upload and test your skill

1. In Claude, open Settings → Capabilities and make sure Code execution and file creation is on. On Team and Enterprise plans, an Owner turns this on for the organization.
2. Go to Customize → Skills, upload the zip, and turn the skill on.
3. Test it with a real request that matches the description. If Claude doesn’t pick it up, make the description more specific, or type / in the message box and choose the skill by name.
4. Use it on real work for a week and tighten the instructions wherever you keep correcting the output.

Don’t unzip the file before uploading. Claude expects a zip containing a folder with the skill’s name, with SKILL.md inside it, which is exactly what this tool produces. If you build a zip yourself, compress the folder, not the files inside it.

The rules this tool checks

Claude skills follow the open Agent Skills specification. The builder checks the requirements as you type:

• Name: 1 to 64 characters; lowercase letters, numbers, and hyphens only; no hyphen at the start or end and no double hyphens. It must match the folder name, which the download handles for you.
• Description: required, up to 1,024 characters. It should say both what the skill does and when to use it.
• Length: Anthropic recommends keeping SKILL.md under 500 lines. If yours is longer, move reference material into separate files and point to them from the instructions.

The description is written into the file as a quoted value, so colons, quotes, and other punctuation won’t break the file, a common problem with hand-written skills.

Writing a description that works

Claude decides whether to use a skill by reading only its description, so a vague description means a skill that never runs. Compare these two:

• Weak: “Helps with emails.” It doesn’t say which emails, what the skill does to them, or when it applies, so Claude can’t tell it apart from an ordinary request.
• Strong: “Write a follow-up email to a client after a meeting, using our house voice and format. Use when the user asks for a follow-up, recap, or thank-you email, or pastes meeting notes and asks what to send.” It names the task, the situation, and the words people actually use.

A good test: imagine three different ways a colleague might ask for this task, and make sure the description contains the key words from all three. If Claude still doesn’t pick the skill up, you can always type / in the message box and choose it by name while you refine the wording.

Ideas for your first skill

• Brand voice: your tone, words you never use, and formatting rules, so every draft sounds like your business.
• Weekly report: the exact sections, order, and level of detail your team or client expects.
• Quote or proposal: your standard structure, the terms you always include, and what to leave for you to fill in.
• Customer replies: how you answer common questions, complaints, and review responses.
• Document review: a checklist Claude runs through when you ask it to review a contract, lease, or vendor agreement, flagging items for you to check rather than giving legal advice.

Not sure what to put in the instructions? Start with one of the templates in our Claude prompt builder; a prompt you reuse every week is a skill waiting to happen.

Skills vs. Projects vs. prompts

A prompt is for one conversation. A Project holds background knowledge, like files about a client, that’s loaded in every chat inside that project. A skill is a procedure Claude loads only when a task matches, in any conversation. Use a skill for “how we do this task,” and a Project for “what you need to know about this client or topic.” Our plain-English guide to Claude skills goes deeper, including how skills relate to connectors and plugins.

A note on safety

Skills you build here contain only the text you wrote. Be more careful with skills from other people: a skill’s instructions and any scripts inside it run as part of your conversation, and Anthropic doesn’t review skills you upload or that someone shares with you. Open every file and read it before turning a shared skill on. And never put passwords or API keys in a skill, because anyone you share it with gets its files.

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