writing-for-agents

writing-for-agents is a skill for Claude Code, Codex from toverux/cantrips. It costs 62 tokens per session (2,835 once invoked), scanned A, a copy of writing-for-agents, MIT.

A writing guide for documents that an AI coding agent will read and follow, such as skills, project instruction files, and rules files. It focuses on clear triggers, predictable processes, and useful pointers to supporting material.

In plain words
What is it for?
Use it when writing or editing agent-facing instructions. It helps shape skill descriptions, routing rules, context pointers, and supporting documentation.
Why use it?
It helps agents reach the right instructions at the right time and follow them consistently. Poorly worded instructions can cause agents to miss required context or load unnecessary material.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present. Also seen: mentions CLAUDE.md; mentions subagents; mentions AGENTS.md.

Part of the cantrips plugin — 24 skills shipped together

Good fit Use it when writing or editing agent-facing instructions. It helps shape skill descriptions, routing rules, context pointers, and supporting documentation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/toverux/cantrips/writing-for-agents
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.

Any agent
npx skills add toverux/cantrips --skill writing-for-agents
Clone the repo
git clone --depth 1 https://github.com/toverux/cantrips

Made for: Claude Code, Codex.

Or install cantrips, the plugin that ships this one along with the rest of its 24 skills.

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-for-agents

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/toverux/cantrips/writing-for-agents"><img src="https://agentmods.dev/badge/skills/toverux/cantrips/writing-for-agents.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,835 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 88% 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 $0.00062 $0.02835
Opus 5 $0.00031 $0.01418
Sonnet 5 $0.00012 $0.00567
Haiku 4.5 $0.00006 $0.00283

Measured 5d ago against content hash 73719a14acb0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

writing-for-agents 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.

Origin

This is a copy

88% identical to writing-for-agents — 74 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.

skills/writing-for-agents/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Reference for writing any document an agent consumes — a skill, an AGENTS.md / CLAUDE.md, a doc reached by a pointer. The packaging differs; the writing does not: the same levers make each one predictable — the agent taking the same process every run, not producing the same output.

When the document you're writing is a skill, read SKILL-MECHANICS.md for the invocation choice and router skills.

Context pointers

A context pointer is a reference held in the agent's context that names some out-of-context material and encodes the condition for reaching it. A skill's description is one; a line in AGENTS.md naming a doc is the same object. The pointer's wording, not its target, decides when the agent reaches the material — and how reliably. A must-have target behind a weakly worded pointer is a variance bug: sharpen the wording first, and inline the material only if sharpening fails.

A pointer does two jobs — state what the material is, and list the branches that should trigger reaching it (a branch is a distinct case the document handles, so different runs take different paths through it). Every word of an always-loaded pointer costs on every turn, so it earns even harder pruning than the body:

  • Front-load the leading word — the pointer is where it does its triggering work.
  • One trigger per branch. Synonyms that rename a single branch are one branch written twice; collapse them and keep only genuinely distinct branches.
  • Cut identity the body already carries.

The two loads

Every document and pointer you add spends one of two budgets:

  • Context load — the cost of always-loaded material on the agent's window: an AGENTS.md line, a skill description, anything sitting in context every turn, spending tokens and attention whether or not it fires.
  • Cognitive load — the cost on the human: which documents exist and when to reach for each. The human is the index. Not a cost to minimise — it is the price of human agency; spend it where human judgement matters, remove it where it does not.

Read the full file on GitHub · 102 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. 5d ago Changed 73719a14acb0
  2. 10d ago First seen · 102 lines · 62 tokens per session scan A ec48566c310c

Subscribe to this mod's changes

writing-for-agents is a skill published in the GitHub repository toverux/cantrips (2 stars, last pushed 7d ago), licensed MIT. It adds 62 tokens to every session and 2,835 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 88% identical to writing-for-agents, differing in 74 lines, and is treated as a copy.

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