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.
npx skills add yz5e/agent-skills --skill opus-4-7-prompt-writergit clone --depth 1 https://github.com/yz5e/agent-skillsWrote 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.
[](https://agentmods.dev/skills/yz5e/agent-skills/opus-4-7-prompt-writer)<a href="https://agentmods.dev/skills/yz5e/agent-skills/opus-4-7-prompt-writer"><img src="https://agentmods.dev/badge/skills/yz5e/agent-skills/opus-4-7-prompt-writer/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.
<a href="https://agentmods.dev/skills/yz5e/agent-skills/opus-4-7-prompt-writer"><img src="https://agentmods.dev/badge/skills/yz5e/agent-skills/opus-4-7-prompt-writer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00087 | $0.01816 |
| Opus 5 | $0.00044 | $0.00908 |
| Sonnet 5 | $0.00017 | $0.00363 |
| Haiku 4.5 | $0.00009 | $0.00182 |
Grade A, and why
opus-4-7-prompt-writer 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 12d 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.
How it starts
The opening of the file, as written. The whole thing — 175 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Opus 4.7 Prompt Writer
Write one prompt that another Claude model can execute with minimal ambiguity. Optimize for action, persistence, and verification, not for prose elegance.
Read references/anthropic-claude-prompting.md when the task is long-horizon, tool-heavy, or expensive enough that prompt quality matters materially.
Workflow
- Capture the real task.
- Identify the execution environment.
- Define hard constraints and done criteria.
- Decide whether the prompt must explicitly push tool use, persistence, and validation.
- Write the prompt in XML-style sections.
- Add an execution loop and verification gate.
- Remove vague or conflicting instructions.
Capture The Real Task
Before writing the prompt, extract:
- The objective: what must be changed, fixed, implemented, or reviewed.
- The environment: repo path, branch, local services, tools, runtime, secrets assumptions.
- The constraints: files or systems that must not be touched, style rules, required docs, approval limits.
- The validation surface: tests, build, lint, integration suites, smoke checks, manual verification, or whatever the project actually uses. Let the user name their own checks instead of assuming any specific stack.
- The completion rule: what must be true before the model may stop.
If the user supplied a spec or earlier review findings, turn those into explicit required work items. Do not leave them implicit.
Prompt Shape
Use XML-like sections because Claude responds well to explicit structure:
<role>: who the model is for this task.<mission>: the concrete outcome.<context>: repo, branch, docs, prior findings, environment.<requirements>: the non-negotiables.<workflow>: the order of work.<tooling>: how and when to use tools.<validation>: exact commands and checks.<done>: stop condition.<output>: how to report results.
Use short, imperative bullets inside each section. Keep the prompt concrete.
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.
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.
- 12d ago First seen · 175 lines · 87 tokens per session scan A 81845e085d22
opus-4-7-prompt-writer is a skill published in the GitHub repository yz5e/agent-skills (16 stars, last pushed 4mo ago), licensed MIT. It adds 87 tokens to every session and 1,816 once invoked, about $0.0004 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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