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 gpt-5-5-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/gpt-5-5-prompt-writer)<a href="https://agentmods.dev/skills/yz5e/agent-skills/gpt-5-5-prompt-writer"><img src="https://agentmods.dev/badge/skills/yz5e/agent-skills/gpt-5-5-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/gpt-5-5-prompt-writer"><img src="https://agentmods.dev/badge/skills/yz5e/agent-skills/gpt-5-5-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 | $0.00090 | $0.02410 |
| Opus 5 | $0.00045 | $0.01205 |
| Sonnet 5 | $0.00018 | $0.00482 |
| Haiku 4.5 | $0.00009 | $0.00241 |
Grade A, and why
gpt-5-5-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 — 216 lines — stays where its author put it; the contents beside it link to each section on GitHub.
GPT-5.5 Prompt Writer
Write one prompt that a GPT-5.5 session can execute with minimal ambiguity. Optimize for outcome, action, persistence, and verification, not for prose elegance.
Read references/openai-gpt-5-5-prompting.md when the task is long-horizon, tool-heavy, or expensive enough that prompt quality materially matters.
Workflow
- Capture the real task.
- Identify the execution environment (Codex CLI, Responses API, Agents SDK, custom harness).
- Define hard constraints and done criteria.
- Decide which Codex-style XML blocks the task actually needs.
- Write the prompt as block-structured XML with an outcome-first task statement.
- Add a verification loop and completeness contract for execution prompts.
- Recommend
reasoning.effortandtext.verbositydeliberately. - Remove vague or contradictory instructions.
Capture The Real Task
Before drafting, extract:
- The objective: what must be changed, fixed, implemented, or reviewed.
- The environment: repo path, branch, services, runtime, tools available, 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.
- The completion rule: what must be true before GPT-5.5 may stop.
If the user supplied a spec or earlier review findings, turn those into explicit required work items in <task>. Do not leave them implicit.
Prompt Shape
GPT-5.5 prompts compose from named XML blocks. Use only the blocks the task needs.
Core wrapper:
<task>— the concrete job, the relevant repo or failure context, and the expected end state.
Output and format:
<structured_output_contract>— exact response shape and ordering.<compact_output_contract>— concise prose contract when no schema applies.
Follow-through and completion:
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 · 216 lines · 90 tokens per session scan A cf6994122097
gpt-5-5-prompt-writer is a skill published in the GitHub repository yz5e/agent-skills (16 stars, last pushed 4mo ago), licensed MIT. It adds 90 tokens to every session and 2,410 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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