Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add skilletmd/skillet --skill write-a-skillgit clone --depth 1 https://github.com/skilletmd/skilletWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/skilletmd/skillet/write-a-skill)<a href="https://agentmods.dev/skills/skilletmd/skillet/write-a-skill"><img src="https://agentmods.dev/badge/skills/skilletmd/skillet/write-a-skill.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00053 | $0.02345 |
| Opus 5 | $0.00026 | $0.01172 |
| Sonnet 5 | $0.00011 | $0.00469 |
| Haiku 4.5 | $0.00005 | $0.00234 |
Grade A, and why
write-a-skill scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.
write-a-skill
A good SKILL.md does one thing well, triggers on the right moment, and stays scoped to what it actually knows. Most skill problems come from: vague trigger descriptions, scope creep, and missing the why.
The minimum viable skill
---
name: my-skill
description: "One sentence. What does this skill do and WHEN should the AI invoke it? Be specific."
---
# my-skill
Instructions for the AI go here.
That's it. Name, description, body. The description is the most important field — it's how the runtime decides whether to load this skill at all.
Frontmatter reference
---
name: my-skill # Required. Slug-format (lowercase, hyphens).
description: "..." # Required. One sentence, specific trigger condition.
# Bad: "Helps with code."
# Good: "Use when reviewing TypeScript PRs for type safety issues."
user-invocable: true # Optional. Adds a /my-skill slash command.
allowed-tools: Bash(git *) # Optional. Restricts which tools the skill can use.
# Omit if the skill only generates text.
---
Writing the description field
The description does two jobs: it tells the runtime when to load the skill, and it tells the user what the skill does.
Bad descriptions (too vague — the runtime loads this for everything):
"Helps with tasks.""Useful for developers.""Context about my project."
Good descriptions (specific trigger condition + what it provides):
"Use when writing or reviewing commit messages to enforce conventional commit format.""Contains my company's refund policy. Trigger when a user asks about returns, refunds, or billing disputes.""Teaches the Skillet sync model. Trigger when someone asks how Skillet works, how to sync skills, or how to add a skill."
The pattern: "Use when [specific situation]. [What the skill provides or does.]"
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 229 lines · 53 tokens per session scan A 31b32e64601e
write-a-skill is a skill published in the GitHub repository skilletmd/skillet (3 stars, last pushed 8d ago), licensed Apache-2.0. It adds 53 tokens to every session and 2,345 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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ijfw-writing-skills
Authoring discipline for new IJFW skills. Use when creating a new skill, writing a skill, making a skill that does X, or asked to add a skill. Trigger: create a new skill, write a skill, new skill, make me a skill, skill that does, /ijfw-writing-skills.