Borrowing it
Nothing to install: this file belongs to a9a4k/tour. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/a9a4k/tour/main/.agents/skills/write-a-skill/SKILL.mdgit clone --depth 1 https://github.com/a9a4k/tourWrote 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/a9a4k/tour/write-a-skill)<a href="https://agentmods.dev/skills/a9a4k/tour/write-a-skill"><img src="https://agentmods.dev/badge/skills/a9a4k/tour/write-a-skill/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/a9a4k/tour/write-a-skill"><img src="https://agentmods.dev/badge/skills/a9a4k/tour/write-a-skill.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00035 | $0.00678 |
| Opus 5.5 | $0.00014 | $0.00271 |
| Sonnet 5.5 | $0.00007 | $0.00136 |
| Haiku 4.5 | $0.00003 | $0.00068 |
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 1mo 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.
This is a copy
94% identical to write-a-skill — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing Skills
Process
-
Gather requirements - ask user about:
- What task/domain does the skill cover?
- What specific use cases should it handle?
- Does it need executable scripts or just instructions?
- Any reference materials to include?
-
Draft the skill - create:
- SKILL.md with concise instructions
- Additional reference files if content exceeds 500 lines
- Utility scripts if deterministic operations needed
-
Review with user - present draft and ask:
- Does this cover your use cases?
- Anything missing or unclear?
- Should any section be more/less detailed?
Skill Structure
skill-name/
├── SKILL.md # Main instructions (required)
├── REFERENCE.md # Detailed docs (if needed)
├── EXAMPLES.md # Usage examples (if needed)
└── scripts/ # Utility scripts (if needed)
└── helper.js
SKILL.md Template
---
name: skill-name
metadata:
internal: true
description: Brief description of capability. Use when [specific triggers].
---
# Skill Name
## Quick start
[Minimal working example]
## Workflows
[Step-by-step processes with checklists for complex tasks]
## Advanced features
[Link to separate files: See [REFERENCE.md](REFERENCE.md)]
Description Requirements
The description is the only thing your agent sees when deciding which skill to load. It's surfaced in the system prompt alongside all other installed skills. Your agent reads these descriptions and picks the relevant skill based on the user's request.
Goal: Give your agent just enough info to know:
- What capability this skill provides
- When/why to trigger it (specific keywords, contexts, file types)
Format:
- Max 1024 chars
- Write in third person
- First sentence: what it does
- Second sentence: "Use when [specific triggers]"
Good example:
Extract text and tables from PDF files, fill forms, merge documents. Use when working with PDF files or when user mentions PDFs, forms, or document extraction.
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.
- 1mo ago First seen · 122 lines · 35 tokens per session scan A 0e3115e2abce
write-a-skill is a skill published in the GitHub repository a9a4k/tour (5 stars, last pushed 4mo ago), licensed MIT. It adds 35 tokens to every session and 678 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 94% identical to write-a-skill, differing in 4 lines, and is treated as a copy.
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