writing-skills

writing-skills is a skill for Claude Code from HECer/yoke. It costs 20 tokens per session (5,053 once invoked), scanned A, a copy of writing-skills, MIT.

A guide for creating and checking reusable instructions for coding agents. It applies test-driven development (TDD), a method of writing a failing test before the solution, to process documentation.

In plain words
What is it for?
Writing, editing, testing, and refining agent skills using pressure scenarios and comparison of results.
Why use it?
It helps reveal whether an instruction guide changes agent behavior before it is deployed.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions subagents.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is ./render-graphs.js ../some-skill # Each diagram separately.

Part of the yoke plugin — 34 skills, 1 hook shipped together

Good fit Writing, editing, testing, and refining agent skills using pressure scenarios and comparison of results.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/HECer/yoke
agentmods
npx agentmods add skills/hecer/yoke/writing-skills

Made for: Claude Code.

Or install yoke, the plugin that ships this one along with the rest of its 34 skills, 1 hook.

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 writing-skills

README.md
[![agentmods](https://agentmods.dev/badge/skills/hecer/yoke/writing-skills/github.svg)](https://agentmods.dev/skills/hecer/yoke/writing-skills)
Your own site
<a href="https://agentmods.dev/skills/hecer/yoke/writing-skills"><img src="https://agentmods.dev/badge/skills/hecer/yoke/writing-skills/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.

agentmods 80×15 button for writing-skills

Your own site · 80×15
<a href="https://agentmods.dev/skills/hecer/yoke/writing-skills"><img src="https://agentmods.dev/badge/skills/hecer/yoke/writing-skills.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,053 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 80% copy Near-identical to another mod 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 5.1 $0.00020 $0.05053
Opus 5 $0.00010 $0.02527
Sonnet 5 $0.00004 $0.01011
Haiku 4.5 $0.00002 $0.00505

Measured 10d ago against content hash 38ba648975ae, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

writing-skills 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 10d 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.

Origin

This is a copy

80% identical to writing-skills — 80 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.

canon/skills/writing-skills/SKILL.md · 656 lines

How it starts

The opening of the file, as written. The whole thing — 656 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing Skills

Overview

Writing skills IS Test-Driven Development applied to process documentation.

Personal skills live in agent-specific directories (~/.claude/skills for Claude Code, ~/.agents/skills/ for Codex)

You write test cases (pressure scenarios with subagents), watch them fail (baseline behavior), write the skill (documentation), watch tests pass (agents comply), and refactor (close loopholes).

Core principle: If you didn't watch an agent fail without the skill, you don't know if the skill teaches the right thing.

REQUIRED BACKGROUND: You MUST understand superpowers:test-driven-development before using this skill. That skill defines the fundamental RED-GREEN-REFACTOR cycle. This skill adapts TDD to documentation.

Official guidance: For Anthropic's official skill authoring best practices, see anthropic-best-practices.md. This document provides additional patterns and guidelines that complement the TDD-focused approach in this skill.

What is a Skill?

A skill is a reference guide for proven techniques, patterns, or tools. Skills help future Claude instances find and apply effective approaches.

Skills are: Reusable techniques, patterns, tools, reference guides

Skills are NOT: Narratives about how you solved a problem once

TDD Mapping for Skills

TDD Concept Skill Creation
Test case Pressure scenario with subagent
Production code Skill document (SKILL.md)
Test fails (RED) Agent violates rule without skill (baseline)
Test passes (GREEN) Agent complies with skill present
Refactor Close loopholes while maintaining compliance
Write test first Run baseline scenario BEFORE writing skill
Watch it fail Document exact rationalizations agent uses
Minimal code Write skill addressing those specific violations
Watch it pass Verify agent now complies
Refactor cycle Find new rationalizations → plug → re-verify

Read the full file on GitHub · 656 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. 10d ago First seen · 656 lines · 20 tokens per session scan A 38ba648975ae

Subscribe to this mod's changes

writing-skills is a skill published in the GitHub repository HECer/yoke (2 stars, last pushed today), licensed MIT. It adds 20 tokens to every session and 5,053 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 80% identical to writing-skills, differing in 80 lines, and is treated as a copy.

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