What is writing-extensions?

A guide for extending Claude Code's configuration explains how to choose between hooks, rules, skills, commands, and agents. It also covers writing descriptions that are correctly selected and testing whether the instructions are followed.

Use it when creating or changing a skill, rule, hook, command, or agent, including through /learn.

It reduces confusion when adding automation under the .claude directory and helps catch extensions that are not being used as intended.

How bheadwei/claude-GUNDAM-zh-tw configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to bheadwei/claude-GUNDAM-zh-tw. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/bheadwei/claude-GUNDAM-zh-tw/main/.claude/skills/writing-extensions/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/bheadwei/claude-GUNDAM-zh-tw

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/bheadwei/claude-gundam-zh-tw/writing-extensions/github.svg)](https://agentmods.dev/skills/bheadwei/claude-gundam-zh-tw/writing-extensions)

Your own site

<a href="https://agentmods.dev/skills/bheadwei/claude-gundam-zh-tw/writing-extensions"><img src="https://agentmods.dev/badge/skills/bheadwei/claude-gundam-zh-tw/writing-extensions/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/bheadwei/claude-gundam-zh-tw/writing-extensions"><img src="https://agentmods.dev/badge/skills/bheadwei/claude-gundam-zh-tw/writing-extensions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,825 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 unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00078	$0.02825
Opus 5.5	$0.00031	$0.01130
Sonnet 5.5	$0.00016	$0.00565
Haiku 4.5	$0.00008	$0.00282

Measured today against content hash fef2ce6a72c0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

writing-extensions 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 today.

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.

.claude/skills/writing-extensions/SKILL.md · 170 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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.

today Changed fef2ce6a72c0
2d ago Changed fc8699a95de0
9d ago Changed 16abbd62c3c0
16d ago Changed d62e29356a38
19d ago Changed fd0e8aa8da2a
1mo ago Changed ba6a6132e63a
1mo ago Changed · +21 lines 7f32ed906c6b
1mo ago First seen · 149 lines · 78 tokens per session scan A c49d1e0803f1

Subscribe to this mod's changes

writing-extensions is a skill published in the GitHub repository bheadwei/claude-GUNDAM-zh-tw (12 stars, last pushed yesterday), with no licence file. It adds 78 tokens to every session and 2,825 once invoked, about $0.0003 per session on Opus 5.5. 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 2026-09-09.

Building agents

writing-extensions next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
writing-extensionsbheadwei/claude-GUNDAM-zh-tw	Skill	12	yesterday	none	A	78	Claude Code
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code

claude-GUNDAM-zh-tw: Skill for Claude Code