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 kotaroyamame/formal-agent-contracts --skill extract-specgit clone --depth 1 https://github.com/kotaroyamame/formal-agent-contractsWrote 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/kotaroyamame/formal-agent-contracts/extract-spec)<a href="https://agentmods.dev/skills/kotaroyamame/formal-agent-contracts/extract-spec"><img src="https://agentmods.dev/badge/skills/kotaroyamame/formal-agent-contracts/extract-spec/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/kotaroyamame/formal-agent-contracts/extract-spec"><img src="https://agentmods.dev/badge/skills/kotaroyamame/formal-agent-contracts/extract-spec.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 | $0.00111 | $0.03346 |
| Opus 5 | $0.00056 | $0.01673 |
| Sonnet 5 | $0.00022 | $0.00669 |
| Haiku 4.5 | $0.00011 | $0.00335 |
Grade A, and why
extract-spec 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 — 329 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Extracting Provisional VDM-SL Specifications from Source Code
Extract structural and behavioral information from existing code and generate a PROVISIONAL VDM-SL specification as a starting point for dialogue with the user.
Critical principle: The spec extracted from code is NOT the true spec. It is a provisional
scaffold for dialogue. The true spec exists in the user's head. Every extracted item must be
tagged [PROVISIONAL] and framed as a question, not a statement.
既存のコードから構造情報と動作情報を抽出し、ユーザーとの対話の出発点となる 暫定的なVDM-SL仕様を生成する。
重要な原則: コードから抽出した仕様は「真の仕様」ではない。それはあくまで対話のための
暫定的な足がかりである。真の仕様はユーザーの頭の中に存在する。抽出した全ての項目には
[PROVISIONAL]というタグをつけ、陳述ではなく質問として表現する。
Dialogue Flow
Step 1: Scope Identification
Ask the user which files or directories to analyze.
Questions to guide the scope:
- Which files or directories should I analyze?
- Are there entry points (main functions, API endpoints)?
- Are there any main modules or key classes I should focus on?
- Are there tests, documentation, or comments that explain the behavior?
ユーザーに、どのファイルまたはディレクトリを分析するかを質問する。
スコープを確定するための質問:
- どのファイルまたはディレクトリを分析すべきか？
- エントリーポイント（メイン関数、APIエンドポイント）はあるか？
- 注目すべきメインモジュールやキークラスはあるか？
- 動作を説明するテスト、ドキュメント、またはコメントはあるか？
Step 2: Structural Analysis
Read the code and extract candidates for:
Data Types
- Classes, interfaces, structs, dataclasses → VDM-SL record type candidates
- Enums → quote union candidates
- Optional/nullable types → optional type
[T]candidates - Union types → VDM-SL union type candidates
- Collections (arrays, lists, sets, maps) → sequence/set/map type candidates
Functions and Operations
- Function/method signatures → VDM-SL function/operation candidates
- Parameters and return types → type mappings
- State mutations (if any) → operation vs. function classification
Constraints and Validation Logic
- If-guards, assertions, validation functions → pre-condition candidates
- Return value patterns and state postconditions → post-condition candidates
- Invariants, decorators, schema validators → invariant candidates
- Test assertions → implicit specification evidence
What ships with it
1 file 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 · 329 lines · 111 tokens per session scan A 08cfe20f9fe4
extract-spec is a skill published in the GitHub repository kotaroyamame/formal-agent-contracts (1 stars, last pushed 2mo ago), licensed MIT. It adds 111 tokens to every session and 3,346 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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