What is contract-notary?

A validator for the input and output agreements between coding-agent skills. These agreements describe what one skill needs and what another skill provides, including the expected data types.

Use it to audit two skills or a multi-skill workflow, generate missing input/output contracts, and recommend bridge steps where data does not line up.

It catches mismatched assumptions before skills are chained together. This helps identify missing steps when one skill's output cannot satisfy another's input.

contract-notary — Skill for Claude Code and Codex by johntimothybailey

Install

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.

Any agent

npx skills add johntimothybailey/skill-harbor --skill contract-notary

Clone the repo

git clone --depth 1 https://github.com/johntimothybailey/skill-harbor

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/johntimothybailey/skill-harbor/contract-notary/github.svg)](https://agentmods.dev/skills/johntimothybailey/skill-harbor/contract-notary)

Your own site

<a href="https://agentmods.dev/skills/johntimothybailey/skill-harbor/contract-notary"><img src="https://agentmods.dev/badge/skills/johntimothybailey/skill-harbor/contract-notary/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/johntimothybailey/skill-harbor/contract-notary"><img src="https://agentmods.dev/badge/skills/johntimothybailey/skill-harbor/contract-notary.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 389 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00044	$0.00389
Opus 5	$0.00022	$0.00195
Sonnet 5	$0.00009	$0.00078
Haiku 4.5	$0.00004	$0.00039

Measured 10d ago against content hash 18a36610d7b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

contract-notary 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 10d 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.

toolkit-repository/contract-notary/SKILL.md · 40 lines

What it actually says

Skill: Contract Notary 📜

You are the Contract Notary of the Skill Harbor. Your mission is to ensure that the contracts ('Engagements') between skills are semantically compatible.

🧭 Guidelines

Semantic Matching:
- Do not just match property names (e.g., results and search_results).
- Use Agent Reasoning to determine if the content produced by an upstream skill satisfies the context required by a downstream skill.
Contract Generation:
- Automatically generate ## Requires and ## Produces sections for any existing skill based on its logic.
- Use the standard syntax: - variable_name: Description (Type)
Chain Validation:
- If a 'Voyager' involves multiple skills, audit the entire path to ensure data flow is uninterrupted.

🛠️ Usage Example

"I want to pass the output of 'NPM Search' to 'Vite Deploy'." Notary: "NPM Search produces 'packageinfo', but Vite Deploy requires 'project_root'. We need an intermediate 'clone' skill."

Requires

skill_a_path: Source skill for analysis.
skill_b_path: Target skill for integration.

Produces

notary_audit: A pass/fail report with semantic reasoning.
bridge_recommendation: Suggestion for bridge skills if needed.

Changes

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.

10d ago First seen · 40 lines · 44 tokens per session scan A 18a36610d7b1

Subscribe to this mod's changes

contract-notary is a skill published in the GitHub repository johntimothybailey/skill-harbor (4 stars, last pushed 3mo ago), licensed MIT. It adds 44 tokens to every session and 389 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 2026-08-31.

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