authoring-claude-md

authoring-claude-md is a skill for Claude Code, Codex from sammcj/agentic-coding. It costs 93 tokens per session (2,269 once invoked), scanned A, original, Apache-2.0.

Guidance for creating and maintaining CLAUDE.md and .claude/rules files, which store project-specific instructions and context for AI coding agents. It focuses on non-obvious conventions, architecture decisions, and recurring problems.

In plain words
What is it for?
Use it to document codebase conventions, architectural patterns, known pitfalls, testing practices, and path-specific instructions.
Why use it?
It helps agents follow important project rules without repeatedly rediscovering or asking about them.

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/sammcj/agentic-coding/authoring-claude-md
Any agent
npx skills add sammcj/agentic-coding --skill authoring-claude-md
Clone the repo
git clone --depth 1 https://github.com/sammcj/agentic-coding

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 authoring-claude-md

README.md
[![agentmods](https://agentmods.dev/badge/skills/sammcj/agentic-coding/authoring-claude-md.svg)](https://agentmods.dev/skills/sammcj/agentic-coding/authoring-claude-md)
Your own site
<a href="https://agentmods.dev/skills/sammcj/agentic-coding/authoring-claude-md"><img src="https://agentmods.dev/badge/skills/sammcj/agentic-coding/authoring-claude-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 93 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,269 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 $0.00093 $0.02269
Opus 5 $0.00046 $0.01135
Sonnet 5 $0.00019 $0.00454
Haiku 4.5 $0.00009 $0.00227

Measured 5d ago against content hash 6cc8f9cb56c9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

authoring-claude-md 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 5d 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/authoring-claude-md/SKILL.md · 220 lines

How it starts

The opening of the file, as written. The whole thing — 220 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md and Rules Authoring

Create effective CLAUDE.md files and .claude/rules/ rule files that serve as project-specific memory for AI coding agents.

Purpose

CLAUDE.md files and rule files provide AI agents with:

  • Non-obvious conventions, architectural patterns and gotchas
  • Confirmed solutions to recurring issues
  • Project-specific context not found in standard documentation
  • Path-scoped instructions that only load when relevant files are touched

Not for: obvious patterns, duplicating documentation, or generic coding advice.

Core Principles

  • Signal over noise: Every sentence must add non-obvious value. If an AI agent could infer it from reading the codebase, omit it.
  • Actionable context: Focus on "what to do" and "why it matters", not descriptions of what exists.
  • Solve real friction, not theoretical concerns: Add to CLAUDE.md based on actual problems encountered, not hypothetical scenarios. If you repeatedly explain the same thing to Claude, document it. If you haven't hit the problem yet, don't pre-emptively solve it.

Structure

Use headings for clear organisation. Common sections: Architecture, Conventions, Gotchas, Testing. Use 2-4 sections and only include what adds value.

When to Use .claude/rules/ Instead

For larger projects, break instructions into separate files under .claude/rules/. Each .md file covers one topic. Prefer rules over a single CLAUDE.md when:

  • Instructions are growing beyond 200 lines
  • Different rules apply to different parts of the codebase (frontend vs backend, API vs CLI)
  • Multiple team members maintain different sections
  • Some instructions only matter when working with specific file types

Rule File Basics

your-project/
├── .claude/
│   ├── CLAUDE.md           # Main project instructions
│   └── rules/
│       ├── code-style.md   # Always loaded
│       ├── testing.md      # Always loaded
│       └── security.md     # Always loaded

Files are discovered recursively, so subdirectories like frontend/ and backend/ work. Rules without paths frontmatter load at launch with the same priority as .claude/CLAUDE.md.

Read the full file on GitHub · 220 lines

Files

What ships with it

2 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. 5d ago First seen · 220 lines · 93 tokens per session scan A 6cc8f9cb56c9

Subscribe to this mod's changes

authoring-claude-md is a skill published in the GitHub repository sammcj/agentic-coding (159 stars, last pushed yesterday), licensed Apache-2.0. It adds 93 tokens to every session and 2,269 once invoked, about $0.0005 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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