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 OutlineDriven/odin-claude-plugin --skill contract-drivengit clone --depth 1 https://github.com/OutlineDriven/odin-claude-pluginWrote 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/outlinedriven/odin-claude-plugin/contract-driven)<a href="https://agentmods.dev/skills/outlinedriven/odin-claude-plugin/contract-driven"><img src="https://agentmods.dev/badge/skills/outlinedriven/odin-claude-plugin/contract-driven/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/outlinedriven/odin-claude-plugin/contract-driven"><img src="https://agentmods.dev/badge/skills/outlinedriven/odin-claude-plugin/contract-driven.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- 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 | $0.00033 | $0.00804 |
| Opus 5.5 | $0.00013 | $0.00322 |
| Sonnet 5.5 | $0.00007 | $0.00161 |
| Haiku 4.5 | $0.00003 | $0.00080 |
Grade A, and why
contract-driven 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 1mo 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- design-by-contract — 92% identical, 153 lines differ
- design-by-contract — 92% identical, 153 lines differ
How it starts
The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Contract-driven
Contract
| Field | Bound contract |
|---|---|
| Trigger | Crossing a public API boundary, guarding complex invariants, or hardening untrusted input or integration seams. |
| Authority | Reversible local: writes only named local types, assertions, validators, and tests at contract boundaries; rollback is undo (delete the added code or revert the boundary change). No remote mutation. |
| Side effect | Adds or refines local types, assertions, validators, and tests at contract boundaries. |
| Done | Every planned contract is implemented at the appropriate static/test/debug/runtime layer and violations fail explicitly at the boundary. |
Inputs
Required:
- The requirements or specification for the operation whose contract is being designed.
- The target source file or module containing the public API boundary, invariant, or untrusted seam.
Optional:
- Existing tests that must continue to pass.
Procedure
- Plan: extract PRE/POST/INV from the requirements. Give each contract an ID and a one-line description (e.g. PRE-1: amount > 0; POST-1: balance == old(balance) - amount; INV-1: balance >= 0). Do not begin implementation until every planned contract has an ID. Done when: every planned contract has an ID and a one-line description.
- Select verification level: choose the strongest layer that can enforce each contract, preferring static over runtime:
- Static type system or static_assert for type size, alignment, null/type safety, and exhaustiveness.
- Test assertions for expensive O(n)+ properties.
- Debug-only invariants for internal invariants.
- Runtime guards for public API input, and always for external or untrusted input. If a property can be verified statically, do not add a runtime contract. Done when: every contract has a selected verification level, static preferred over runtime.
- Create: implement every PRE, POST, INV at its chosen level in the target local code. Runtime contracts, where used, must be active and not compiled out or disabled. Done when: every contract is implemented at its chosen level and runtime contracts are active.
- Verify: run the type checker, static analysis, and build. Contracts must compile and lint. Done when: the type checker, static analysis, and build pass with all contracts.
- Test: write one violation test per PRE/POST/INV proving the contract catches bad input or bad state. Static contracts are verified by the type checker; runtime contracts by violation tests that assert the boundary fails explicitly. Done when: one violation test per contract passes, proving the boundary fails on bad input or state.
What ships with it
3 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.
- 1mo ago Changed · -19 tokens per session 50a4c22ee2e6
- 1mo ago Changed · -77 lines · +18 tokens per session 1d1fb117abd0
- 1mo ago First seen · 128 lines · 34 tokens per session scan A 0d71ed2b9bec
contract-driven is a skill published in the GitHub repository OutlineDriven/odin-claude-plugin (37 stars, last pushed 21d ago), licensed Apache-2.0. It adds 33 tokens to every session and 804 once invoked, about $0.0001 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.
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