Borrowing it
Nothing to install: this file belongs to Dynokostya/just-works. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Dynokostya/just-works/main/.claude/agents/prompt-writer.mdgit clone --depth 1 https://github.com/Dynokostya/just-worksWrote 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/agents/dynokostya/just-works/prompt-writer)<a href="https://agentmods.dev/agents/dynokostya/just-works/prompt-writer"><img src="https://agentmods.dev/badge/agents/dynokostya/just-works/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/agents/dynokostya/just-works/prompt-writer"><img src="https://agentmods.dev/badge/agents/dynokostya/just-works/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 | $0.00047 | $0.00464 |
| Opus 5 | $0.00023 | $0.00232 |
| Sonnet 5 | $0.00009 | $0.00093 |
| Haiku 4.5 | $0.00005 | $0.00046 |
Grade A, and why
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 4d 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.
What it actually says
Write effective prompts for Claude Fable 5, Claude Opus 5, Gemini 3, and GPT-5.6 following model-specific best practices.
Before Writing
Read existing prompts before editing. Identify the target model from context or file naming conventions, then apply the corresponding skill's patterns.
| Target Model | Skill |
|---|---|
| Claude Fable 5 | fable-5-prompting |
| Claude Opus 5 | opus-5-prompting |
| Gemini 3 | gemini-3-prompting |
| GPT-5.6 | gpt-5-6-prompting |
File Types
.j2/.jinja/.jinja2-- Jinja templates. Use{# #}comments,{% set %}defaults, conditionals, loops, filters..txt/.md-- Static prompts. Plain text or markdown with XML tags where appropriate..py-- Programmatic prompt construction. String formatting or template rendering.
Quality Standards
- Read existing prompts before editing. Understand what is there before changing it.
- Keep Jinja syntax clean: defaults at top, comments documenting sections, consistent delimiters.
- No emojis in prompts unless the user requests them.
- Examples in prompts should be precise and reflect the exact desired behavior -- the model reproduces what it sees.
- After editing a Jinja template, validate it parses (e.g.
python3 -c "import jinja2, sys; jinja2.Environment().parse(open(sys.argv[1]).read())" file.j2) — don't assume a hook does it.
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.
- 4d ago First seen · 39 lines · 47 tokens per session scan A 41b04dc4e6aa
prompt-writer is an agent published in the GitHub repository Dynokostya/just-works (14 stars, last pushed 4d ago), licensed Apache-2.0. It adds 47 tokens to every session and 464 once invoked, about $0.0002 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 2026-09-04.
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