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 dayfinggg/openai-codex-agent-skills --skill api-contract-changegit clone --depth 1 https://github.com/dayfinggg/openai-codex-agent-skillsWrote 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/dayfinggg/openai-codex-agent-skills/api-contract-change)<a href="https://agentmods.dev/skills/dayfinggg/openai-codex-agent-skills/api-contract-change"><img src="https://agentmods.dev/badge/skills/dayfinggg/openai-codex-agent-skills/api-contract-change/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/dayfinggg/openai-codex-agent-skills/api-contract-change"><img src="https://agentmods.dev/badge/skills/dayfinggg/openai-codex-agent-skills/api-contract-change.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 | $0.00038 | $0.00344 |
| Opus 5.5 | $0.00015 | $0.00138 |
| Sonnet 5.5 | $0.00008 | $0.00069 |
| Haiku 4.5 | $0.00004 | $0.00034 |
Grade A, and why
api-contract-change 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 today.
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.
What it actually says
Preserve the API behavior that existing clients and integrations rely on.
- Read the requested outcome, endpoint implementation, schema or OpenAPI definition, callers, middleware, and relevant tests. Establish method, route, payload, response, and accepted event types.
- Identify untrusted inputs and validate at the owning boundary. Preserve distinctions among malformed input, authentication failure, authorization denial, not found, and internal failure where the contract exposes them.
- Treat source authentication, user-access policy, and supported events as separate decisions. A signature or token fix does not authorize restricting users or dropping accepted event types.
- Trace data transformations through application and persistence boundaries. Check content types, encoding, nullability, pagination, idempotency, and version compatibility only where the change touches them.
- Implement the smallest compatible behavior. Keep internal exceptions and secrets out of client errors while retaining diagnostic context in the existing logging system.
- Verify success and the material rejection or failure paths. Check status, headers, body shape, side effects, and the unchanged client behavior.
- Update an existing API contract artifact when the requested behavior changes it. Do not create unrelated documentation or a new API version merely to record a local fix.
Use the relevant language and framework specialist. For schema or security mechanisms, read the actual installed framework's official documentation and the existing integration contract.
Finish when the requested contract is implemented and verified. Identify a genuinely incompatible change before applying dependent work if user intent cannot resolve it.
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.
- today First seen · 20 lines · 38 tokens per session scan A eaa4ac417d13
api-contract-change is a skill published in the GitHub repository dayfinggg/openai-codex-agent-skills (8 stars, last pushed today), licensed MIT. It adds 38 tokens to every session and 344 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 2026-10-30.
Other skills, from other repositories
coco-delivery
Implement and verify CoCo features end-to-end (Telegram commands, callbacks, app-server transport, queueing, watchdogs, approvals, and tests). Use when changing this repository's bot behavior and needing repo-specific file targets, workflows, and validation commands. NOT for generic Python tasks outside CoCo.
api-contract-checker
Validate API changes against an expected contract. Use when a mid-level developer needs to detect breaking changes.
api-testing-observability-api-mock
You are an API mocking expert specializing in realistic mock services for development, testing, and demos. Design mocks that simulate real API behavior and enable parallel development.
k6
Generate, validate, and review k6 test scripts — load, stress, spike, soak, smoke, breakpoint, functional, and protocol. Covers HTTP, WebSocket, gRPC, browser, all executors, thresholds, checks, custom metrics, the k6-testing library, k6 Cloud execution, and the xk6 extension ecosystem; uses the xk6-docs CLI (with…
worker-backend-dev
Cortex delegated specialist only: Backend implementation specialist for APIs, business logic, persistence, and server-side tests.
mem0-test-integration
Verify a Mem0 integration produced by /mem0-integrate. Runs in the same workspace on the same branch (loose coupling) — installs dependencies, runs the repo's native test suite, then exercises a real end-to-end smoke flow against the user's API key. Produces a scorecard. TRIGGER when: user has just run /mem0-integrate…