What is writing-agent-prompt?

A writing guide for model-facing instructions such as AGENTS.md files, system prompts, and prompt rules. It focuses on wording that tells an agent what action and final result to produce.

Use it when revising agent instructions, especially when checking that the agent starts the task, researches missing details, continues through recoverable problems, and reports the result.

Poorly worded instructions can make an agent explain, ask for permission, or stop instead of doing authorized work. The guide also requires testing prompt changes with realistic response probes.

writing-agent-prompt — Skill by companion-inc/introspect

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 companion-inc/introspect --skill writing-agent-prompt

Clone the repo

git clone --depth 1 https://github.com/companion-inc/introspect

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/companion-inc/introspect/writing-agent-prompt/github.svg)](https://agentmods.dev/skills/companion-inc/introspect/writing-agent-prompt)

Your own site

<a href="https://agentmods.dev/skills/companion-inc/introspect/writing-agent-prompt"><img src="https://agentmods.dev/badge/skills/companion-inc/introspect/writing-agent-prompt/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/companion-inc/introspect/writing-agent-prompt"><img src="https://agentmods.dev/badge/skills/companion-inc/introspect/writing-agent-prompt.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 632 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 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.

Model	Per session	Once invoked
Fable 5.1	$0.00068	$0.00632
Opus 5.5	$0.00027	$0.00253
Sonnet 5.5	$0.00014	$0.00126
Haiku 4.5	$0.00007	$0.00063

Measured 2mo ago against content hash fe327e9e3154, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

writing-agent-prompt 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 2mo 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/writing-agent-prompt/SKILL.md · 43 lines

How it starts

The opening of the file, as written. The whole thing — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing Agent Prompt

Purpose

Use this skill for prompt wording after agent-md-creator has decided that the behavior belongs in an always-loaded prompt. This skill is about phrasing and behavioral verification, not placement.

Procedure

Read the failure transcript and name the unwanted model move in one sentence.
Write the desired first move and final artifact in plain behavioral terms.
Rewrite the instruction with action verbs such as produce, implement, continue, substitute, verify, and report.
Put research requirements inside the action path: the model should discover missing details with tools while moving toward the artifact.
If a sub-action cannot run, phrase the recovery as substitution and continuation.
Verify by probing the actual agent with a realistic prompt from the failure and reading the response for behavior. The response should start the work, name the first concrete action, and avoid asking for permission when authorization is already present.
If the probe fails, revise the prompt and probe again. Do not replace the behavioral test with a text-matching proxy.

Gotchas

A prompt can match expected words and still fail behaviorally. Judge the response, not isolated text.
A text-matching proxy can block legitimate prompt text while missing the same failure expressed another way.
Prefer "answer with the changed artifact and verification" over naming every bad response style.
A hidden or empty skill folder is not a skill. It needs SKILL.md frontmatter and an index entry so the reflector can route to it.
Do not blindly obey this skill when the edited prompt is for a regulated product workflow; read the product docs and verify the result against the real prompt file.

Verification

Run at least one behavior probe against the actual agent runtime that loads the edited prompt.
Run ./scripts/validate-skills.py after creating or changing this skill.
For core prompt edits, run ./scripts/introspect-status.sh and confirm Claude and Codex prompt links target the edited file.

Read the full file on GitHub · 43 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.

2mo ago First seen · 43 lines · 68 tokens per session scan A fe327e9e3154

Subscribe to this mod's changes

writing-agent-prompt is a skill published in the GitHub repository companion-inc/introspect (10 stars, last pushed 2mo ago), licensed MIT. It adds 68 tokens to every session and 632 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 2026-08-31.

Data and AI Prompting Writing and docs

writing-agent-prompt next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
writing-agent-promptcompanion-inc/introspect	Skill	10	2mo ago	MIT	A	68	Claude Code, Codex
llm-app-patternsdavila7/claude-code-templates	Skill	33k	yesterday	MIT	A	54	Claude Code, Codex
prompt-engineerJeffallan/claude-skills	Skill	12k	7d ago	MIT	A	93	Claude Code
prompt-optimizationlangwatch/langwatch	Skill	5.0k	yesterday	Apache-2.0	A	105	Claude Code, Codex
omh-model-optimizationrlaope/oh-my-hermes	Skill	5.2k	yesterday	MIT	A	84	Claude Code, Codex
ideogram4digitalsamba/claude-code-video-toolkit	Skill	2.5k	yesterday	MIT	A	99	Claude Code
prompt-library-for-startupsaws/agent-toolkit-for-aws	Skill	3.4k	yesterday	Apache-2.0	A	228	Claude Code