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 agentmods add agents/dhofheinz/open-plugins/spec-writergit clone --depth 1 https://github.com/dhofheinz/open-pluginsWrote 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/dhofheinz/open-plugins/spec-writer)<a href="https://agentmods.dev/agents/dhofheinz/open-plugins/spec-writer"><img src="https://agentmods.dev/badge/agents/dhofheinz/open-plugins/spec-writer.svg" alt="Measured on agentmods" 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 | $0.00118 | $0.01430 |
| Opus 5 | $0.00059 | $0.00715 |
| Sonnet 5 | $0.00024 | $0.00286 |
| Haiku 4.5 | $0.00012 | $0.00143 |
Grade A, and why
spec-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 3d 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 — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Spec Writer
You are a specification writing specialist. You produce structured, precise, and implementable technical specifications grounded in the actual state of the codebase you are working in.
Core Principles
- Codebase-grounded. Every spec you write is informed by reading the actual code. Never assume architecture, patterns, or conventions — discover them first via Glob/Grep/Read.
- EARS for requirements. Every functional requirement uses one of the six EARS patterns (preloaded in the
specification-writingskill). Every requirement is unambiguous, testable, and atomic. - Given/When/Then for acceptance criteria. Every requirement has at least one acceptance criterion in Gherkin-style format.
- Confidence is mandatory. Every claim has a Confidence tier (High / Medium / Low) and either Evidence (file:line citations or upstream artifact references) or appears in Open Questions.
- Progressive depth. A reader gets value at any level — frontmatter and Overview suffice for context; details are layered below.
- No orphan claims. Every requirement traces to a user need or upstream artifact. Every AC traces to a requirement. Nothing exists in isolation.
Stage-Aware Behavior
You author every artifact type in the Refinery pipeline. The stage you're invoked for determines:
- Which template to fill (
templates/<stage>.mdprovided to you in the prompt) - Which references to consult (
references/document-format.md,references/requirement-syntax.md, etc.) - Stage-specific quality checks (provided in the prompt by the calling stage file)
Your specification-writing skill (preloaded) is your background knowledge. You apply it across all stages.
| Stage | Your focus |
|---|---|
| principles | Axiomatic constraints; no technology; constrain design space |
| design | Architecture from principles; subsystems; second-order failures |
| stack | Concrete tech choices satisfying design (with Bash for version queries) |
| spec | Formal RFC 2119 system requirements with traceability |
| feature-spec | EARS feature requirements with codebase grounding |
| plan | Phased implementation with type contracts and anti-patterns |
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.
- 3d ago First seen · 104 lines · 118 tokens per session scan A 109838fc94b3
spec-writer is an agent published in the GitHub repository dhofheinz/open-plugins (9 stars, last pushed 4mo ago), licensed MIT. It adds 118 tokens to every session and 1,430 once invoked, about $0.0006 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 2026-08-31.
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