write-a-skill

write-a-skill is a skill for Claude Code, Codex from kimgoetzke/coding-agent-configs. It costs 35 tokens per session (753 once invoked), scanned A, original, MIT.

A guide for creating a skill that gives an agent instructions for a specific task or area of work. It covers the required SKILL.md file and optional examples, reference documents, scripts, and templates.

In plain words
What is it for?
Use it when building a new skill, deciding what files it needs, or reviewing its instructions with a user. It can support skills that need written guidance, executable helper scripts, or reusable templates.
Why use it?
It provides a clear structure for turning repeatable knowledge or procedures into an agent skill. This helps keep instructions focused and makes extra resources available only when needed.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/kimgoetzke/coding-agent-configs/write-a-skill
Any agent
npx skills add kimgoetzke/coding-agent-configs --skill write-a-skill
Clone the repo
git clone --depth 1 https://github.com/kimgoetzke/coding-agent-configs

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for write-a-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/kimgoetzke/coding-agent-configs/write-a-skill.svg)](https://agentmods.dev/skills/kimgoetzke/coding-agent-configs/write-a-skill)
Your own site
<a href="https://agentmods.dev/skills/kimgoetzke/coding-agent-configs/write-a-skill"><img src="https://agentmods.dev/badge/skills/kimgoetzke/coding-agent-configs/write-a-skill.svg" alt="Measured on agentmods" height="20"></a>
Per session 35 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 753 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00035 $0.00753
Opus 5 $0.00017 $0.00377
Sonnet 5 $0.00007 $0.00151
Haiku 4.5 $0.00003 $0.00075

Measured 3d ago against content hash e756af7a8901, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 3d 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.

skills/write-a-skill/SKILL.md · 121 lines

How it starts

The opening of the file, as written. The whole thing — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing skills

Process

  1. 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?
  2. Draft the skill - create:

    • SKILL.md with concise instructions
    • Additional reference files, if required
    • Utility scripts if deterministic operations needed
  3. 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/               # Scripts (if needed)
│   └── helper-script.sh   # Utility script (if needed)
└── templates/             # Templates (if needed)
    ├── template-1.md
    └── template-2.md

SKILL.md template

---
name: skill-name
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:

  1. What capability this skill provides
  2. 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.

Read the full file on GitHub · 121 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

  1. 3d ago First seen · 121 lines · 35 tokens per session scan A e756af7a8901

Subscribe to this mod's changes

write-a-skill is a skill published in the GitHub repository kimgoetzke/coding-agent-configs (2 stars, last pushed 14d ago), licensed MIT. It adds 35 tokens to every session and 753 once invoked, about $0.0002 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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