skill-authoring

A guide for writing SKILL.md files, which are instruction files that teach AI coding agents when and how to perform a task. It defines the required metadata, trigger phrases, decision guidance, examples and verification checks.

In plain words
What is it for?
Use it to create or revise an agent skill, including its name, description, version, triggers, tags, instructions, decision points and completion checklist.
Why use it?
It helps authors create skills that agents can recognize and follow consistently. It also reduces errors in the file format and in the description that activates a skill.

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/rohitg00/skillkit/skill-authoring
Any agent
npx skills add rohitg00/skillkit --skill skill-authoring
Clone the repo
git clone --depth 1 https://github.com/rohitg00/skillkit

Made for: Claude Code, Codex.

Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,477 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 $0.00072 $0.01477
Opus 5 $0.00036 $0.00739
Sonnet 5 $0.00014 $0.00295
Haiku 4.5 $0.00007 $0.00148

Measured 3d ago against content hash 50315c8d3d22, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

skill-authoring 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.

packages/core/src/methodology/packs/meta/skill-authoring/SKILL.md · 228 lines

How it starts

The opening of the file, as written. The whole thing — 228 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Authoring Guide

You are authoring a SKILL.md for an AI coding agent. A well-written skill provides clear, actionable guidance that agents can follow consistently.

Core Principle

A skill's description triggers it; the body teaches it.

The description tells the agent WHEN to use the skill. The content tells the agent HOW to execute it.

Skill Anatomy

SKILL.md Structure

---
name: [lowercase-hyphenated-name]
description: [Concrete actions + "Use when..." clause]
version: [Semantic version]
triggers:
  - [keyword 1]
  - [keyword 2]
tags:
  - [tag 1]
---

# [Skill Title]

[Introduction paragraph explaining purpose]

## Core Principle

**[Single most important rule in bold]**

## [Main Content Sections]

## [Decision Points]

## [Verification Checklist]

Frontmatter Fields

Field Required Constraints
name Yes Lowercase alphanumeric + hyphens, 1–64 chars
description Yes Must include "Use when..." clause; 1–1024 chars
version Yes Semantic version (e.g. 1.0.0)
triggers Recommended Natural-language phrases that activate the skill
tags Recommended Categorization tags

Writing Effective Triggers

Triggers should be phrases users naturally type.

Good triggers:

  • "write tests first"
  • "tdd"
  • "test driven development"

Bad triggers:

  • "testing methodology" (too vague)
  • "red-green-refactor-cycle-for-test-driven-development" (too specific)
  • "skill-123" (not natural language)

Trigger Guidelines

  1. Natural language — How would a human ask for this?
  2. Multiple variations — Different ways to say the same thing
  3. Specific enough — Don't trigger on too many queries
  4. Common terms — Use terms people actually use

Writing Skill Content

Voice and Tone

Use second person, present tense, active voice:

  • ✅ "Write the test first"
  • ✅ "You are implementing TDD"
  • ❌ "The developer should..." (passive)
  • ❌ "It is recommended that..." (wordy)

Read the full file on GitHub · 228 lines

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 · 228 lines · 72 tokens per session scan A 50315c8d3d22

Subscribe to this mod's changes

skill-authoring is a skill published in the GitHub repository rohitg00/skillkit (1,477 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 72 tokens to every session and 1,477 once invoked, about $0.0004 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 2026-08-30.

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