OpenSpec is a specification-driven development framework that records software requirements and implementation plans as readable Markdown artifacts. It helps developers and AI coding assistants agree on what should be built before code is written, including work spanning multiple repositories. The catalogue add-ons provide workflow skills and instructions for using OpenSpec.
Borrowing it
Nothing to install: this file belongs to Fission-AI/OpenSpec. 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/Fission-AI/OpenSpec/main/.agents/skills/write-openspec-docs/SKILL.mdgit clone --depth 1 https://github.com/Fission-AI/OpenSpecWrote 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/fission-ai/openspec/write-openspec-docs)<a href="https://agentmods.dev/skills/fission-ai/openspec/write-openspec-docs"><img src="https://agentmods.dev/badge/skills/fission-ai/openspec/write-openspec-docs/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/fission-ai/openspec/write-openspec-docs"><img src="https://agentmods.dev/badge/skills/fission-ai/openspec/write-openspec-docs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket warn
- Snyk pass
- NVIDIA SkillSpector pass
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 | $0.00055 | $0.00826 |
| Opus 5.5 | $0.00022 | $0.00330 |
| Sonnet 5.5 | $0.00011 | $0.00165 |
| Haiku 4.5 | $0.00006 | $0.00083 |
Grade A, and why
write-openspec-docs 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.
How it starts
The opening of the file, as written. The whole thing — 35 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Write OpenSpec docs
You are now writing OpenSpec's user docs. Read writing.md; it is the style authority for everything drafted here. The short version, in effect immediately:
- A page is a retrieval surface, not an essay. Structure decides whether the reader finds the answer; prose only decides how it reads. Open every section with the answer, never a running story.
- Choose the page type before the outline. Guides follow the reader's task; reference mirrors the product's structure and uses exact field, command, and file names as scan anchors. Reference needs complete coverage without compressing several facts into one sentence, cell, or paragraph.
- Draft the shortest version that answers; expanding a spare page is cheap, cutting a bloated one is a rewrite. Plain words, the fewest of them: an idea that fits in one line takes one line. Depth most readers skip goes behind a link, and the payload (commands, real output, failures and fixes) stays whole.
- Dumb sentences, smart structure. Write the obvious sentence (actor, verb, object, stating the literal event); never compress extra facts in or take an angle. No hype adjectives, no preamble, no em dashes.
- One job per slot: one fact per sentence, list intros only announce the list, one reader question or lookup target per section. A related fact gets its own slot, never a ride in someone else's.
- Ground items in what the reader can verify: path or folder first, concept as the gloss, real output shown honestly.
- No house template. Inventories open with a list naming every item, then expand each in its own unit after the list, never inline. Sequences take numbered steps (numbers mean order; inventories take bullets). Single ideas and reasoning stay in short prose.
- Every load-bearing fact sits on a scan anchor: code fence, numbered bold lead-in,
**Term**: factbullet, table, file tree. Never only mid-paragraph. - Before finishing, run two backstop tests. Retrievability: can each question or exact product name be found by scanning alone? The glance: inspect the rendered page as shapes; does it look finishable, or like work? Check table-heavy changes at desktop and narrow widths. A failure means a slot got written without being earned; fix it now, don't leave it for review.
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.
- 2mo ago First seen · 35 lines · 55 tokens per session scan A 581e121b2c98
write-openspec-docs is a skill published in the GitHub repository Fission-AI/OpenSpec (74,064 stars, last pushed yesterday), licensed MIT. It adds 55 tokens to every session and 826 once invoked, about $0.0002 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 2026-08-30.
write-openspec-docs compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| write-openspec-docsFission-AI/OpenSpec | Skill | 74k | yesterday | MIT | A | 55 | Claude Code |
| add-community-extensiongithub/spec-kit | Skill | 148k | yesterday | MIT | A | 63 | Claude Code |
| code-reviewgithub/spec-kit | Skill | 148k | yesterday | MIT | A | 54 | Claude Code |
| openprd-harnessmileson/openprd | Skill | 50 | 1mo ago | MIT | A | 68 | Claude Code, Codex |
| openprd-sharedmileson/openprd | Skill | 50 | 1mo ago | MIT | A | 74 | Claude Code, Codex |
| openprd-frontend-designmileson/openprd | Skill | 50 | 1mo ago | MIT | A | 50 | Claude Code, Codex |
| openprd-discovery-loopmileson/openprd | Skill | 50 | 1mo ago | MIT | A | 76 | Codex |