How to write a skill

A skill is a plain text file called SKILL.md. The top of the file is a short front matter block; the rest is markdown instructions that the member's AI reads and follows. The format is open, so a skill you write for Vander Labs works anywhere SKILL.md is supported.

The front matter

Three dashes, two fields, three dashes:

• name: lowercase letters, numbers and hyphens only, no spaces. For example cold-email-review.
• description: one sentence that says when the AI should use this skill. This is the sentence the AI reads to decide whether to load the full instructions, so write it as a trigger, not a slogan. "Use when the user asks to review or rewrite a cold outreach email" works. "The ultimate email skill" does not.

Everything after the front matter is the instructions, in markdown. Keep the whole file under 60,000 characters.

A complete example

---
name: cold-email-review
description: Use when the user asks to review, rewrite or tighten a cold outreach email before sending it.
---

# Cold email review

You are reviewing a cold email the user is about to send to someone who does not know them. Your job is to make it short, specific and easy to say yes to.

## Before you start

Ask for three things if they are not already clear:

1. Who is receiving it (role, company, what they care about).
2. What the sender wants the reader to do (reply, book a call, open a link).
3. Why this reader, now (the trigger: a post, a hire, a launch).

If the user cannot answer the third question, say so plainly. An email without a reason to exist should not be sent yet.

## Rewrite rules

- Under 120 words. Cut until it fits.
- First sentence names the trigger, not the sender.
- One ask, phrased as a question that takes under ten seconds to answer.
- No adjectives about the sender or their product. Show one concrete result instead.
- No "I hope this finds you well", "quick question" or "just following up".
- Subject line: four words or fewer, lowercase, no punctuation.

## Output

Give the user:

1. The rewritten email.
2. The subject line.
3. Three bullets explaining the biggest changes and why.

If the original is already good, say so and change nothing.

## Never

- Never invent facts about the reader or their company.
- Never add urgency that is not real.
- Never write more than one follow-up in the same reply.

What goes in the instructions

• Start with what the AI should do first, usually what to ask the user or what to look at.
• Give the procedure as numbered steps in the order you actually do them.
• Say what good looks like: a checklist, a template, a short before and after.
• Say what never to do. The AI follows these more reliably than general advice.
• Keep it to what a strong colleague would need. If you would not say it out loud to a competent peer, cut it.
• Write for the AI, not for the member. The member never reads SKILL.md in the app; they read your metadata.

Metadata

When you submit on the Creator studio you also fill in: title, subtitle, summary, category, tags, what your AI learns (a few short bullets), steps, safety notes, an optional trailer and a version number. The AI only ever sees the SKILL.md. The metadata is for members browsing the catalog, so write it for people, and make sure it describes what the instructions actually do.

Before you submit

1. Test the skill with at least one supported AI client. Save it to your own library, connect, and run the task it is for.
2. Check that nothing in the file is secret: no API keys, passwords, client names or personal data.
3. Make sure the instructions are yours, or that you have a license that lets you publish them. See the Creator Agreement.
4. Submit. We review every skill before it goes live and leave a review note if we need changes.