write-a-skill

write-a-skill is a skill for Claude Code, Codex from clivechung/skillmcp. It costs 48 tokens per session (1,231 once invoked), scanned A, original, MIT.

A guided process for creating or improving an AI-agent skill, including its instructions, supporting files, examples, and validation.

In plain words
What is it for?
Use it to gather requirements, draft a SKILL.md, review its behavior, refine supporting resources, and place the finished skill in a skills directory.
Why use it?
It helps turn an informal procedure into a clearer, reusable skill with defined triggers and edge-case handling.

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/clivechung/skillmcp/write-a-skill
Any agent
npx skills add clivechung/skillmcp --skill write-a-skill
Clone the repo
git clone --depth 1 https://github.com/clivechung/skillmcp

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/clivechung/skillmcp/write-a-skill.svg)](https://agentmods.dev/skills/clivechung/skillmcp/write-a-skill)
Your own site
<a href="https://agentmods.dev/skills/clivechung/skillmcp/write-a-skill"><img src="https://agentmods.dev/badge/skills/clivechung/skillmcp/write-a-skill.svg" alt="Measured on agentmods" height="20"></a>
Per session 48 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,231 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 $0.00048 $0.01231
Opus 5 $0.00024 $0.00616
Sonnet 5 $0.00010 $0.00246
Haiku 4.5 $0.00005 $0.00123

Measured 2d ago against content hash 044552b3cb2c, 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 2d 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.

.agents/skills/write-a-skill/SKILL.md · 141 lines

How it starts

The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Write A Skill

Guide the user through creating robust, predictable, and token-efficient AI agent skills using Matt Pocock's skill authoring methodology and the standard SKILL.md format.


The 4-Phase Authoring Workflow

Follow these four phases sequentially when authoring or refining a skill:

┌────────────────────────┐
│ 1. Gather Requirements│ ──► Identify domain, use cases, triggers & scripts
└───────────┬────────────┘
            │
            ▼
┌────────────────────────┐
│  2. Draft the Skill    │ ──► Structure SKILL.md, references/, examples/, scripts/
└───────────┬────────────┘
            │
            ▼
┌────────────────────────┐
│  3. Review & Validate  │ ──► Check triggers, edge cases & progressive disclosure
└───────────┬────────────┘
            │
            ▼
┌────────────────────────┐
│      4. Finalize       │ ──► Place in skills/<name>/, link references, test syntax
└────────────────────────┘

Phase 1: Gather Requirements

Before writing any markdown, interview the user to clarify:

  1. Skill Name & Category: What specific problem or capability does this skill address? What category does it belong to (e.g., software, for-fun, or a new domain category)? (Lowercase, hyphenated, matching folder name).
  2. Trigger Criteria: When should the agent reach for this skill? What user prompts, keywords, or workflows should trigger it?
  3. Execution Model:
    • Deterministic Steps: Can repetitive, fragile, or complex commands be encapsulated into scripts (in scripts/)?
    • Procedural Steps: What sequence of actions, decisions, and checks must the agent follow?
  4. Reference Material & Depth:
    • Is there bulky documentation, API specs, or cheatsheets that should be moved into references/ rather than cluttering SKILL.md?
    • Are there concrete input/output examples that belong in examples/?

Phase 2: Draft the Skill

Create the skill directory under skills/<category>/<skill-name>/ (or .agents/skills/<skill-name>/ for workspace meta-skills) with the following structure:

Read the full file on GitHub · 141 lines

Files

What ships with it

3 files 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. 2d ago First seen · 141 lines · 48 tokens per session scan A 044552b3cb2c

Subscribe to this mod's changes

write-a-skill is a skill published in the GitHub repository clivechung/skillmcp (0 stars, last pushed 3d ago), licensed MIT. It adds 48 tokens to every session and 1,231 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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