Borrowing it
Nothing to install: this file belongs to chama-x/GroundRules. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/chama-x/GroundRules/master/.agents/skills/api-contract-tester/SKILL.mdgit clone --depth 1 https://github.com/chama-x/GroundRulesWrote 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/chama-x/groundrules/api-contract-tester)<a href="https://agentmods.dev/skills/chama-x/groundrules/api-contract-tester"><img src="https://agentmods.dev/badge/skills/chama-x/groundrules/api-contract-tester/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/chama-x/groundrules/api-contract-tester"><img src="https://agentmods.dev/badge/skills/chama-x/groundrules/api-contract-tester.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 | $0.00032 | $0.00251 |
| Opus 5.5 | $0.00013 | $0.00100 |
| Sonnet 5.5 | $0.00006 | $0.00050 |
| Haiku 4.5 | $0.00003 | $0.00025 |
Grade A, and why
api-contract-tester 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.
What it actually says
API Contract Tester
You are an expert in API Contract Testing.
1. Schema-Driven Testing
- Always use OpenAPI 3.x or GraphQL schemas as the absolute source of truth.
- Generate mock responses directly from the schema definitions using tools like Prism or WireMock.
2. Preventing Drift
- Implement Consumer-Driven Contract Testing (e.g., Pact) to ensure backend API changes do not break frontend consumers.
- Run drift-detection scripts in CI that compare the generated schema hash against the committed schema.
3. Breaking Change Checks
- Use
openapi-difforgraphql-inspectorin PR pipelines to fail builds if a breaking change (e.g., removing a field, making an optional field required) is detected without a major version bump.
4. Multi-language Client Generation
- Use
openapi-generator-cliorgraphql-codegento automatically regenerate SDKs. - Ensure generated clients are strongly typed and handle network errors gracefully.
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 First seen · 24 lines · 32 tokens per session scan A 339a30d7d20a
api-contract-tester is a skill published in the GitHub repository chama-x/GroundRules (5 stars, last pushed 2mo ago), licensed MIT. It adds 32 tokens to every session and 251 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 2026-08-31.
Other skills, from other repositories
backend-manual-testing
Use when the task touches a backend API, database or worker - booting it from the task branch, driving real requests and verifying side effects (DB rows, outbound calls, logs) as evidence.
worker-job-testing
Use when the task has a background job, queue consumer, scheduler or webhook - firing the real trigger, polling for the side effect, and the retry, idempotency and poison-message cases.
backend-runtime-check
Use before handing off any change to an endpoint, job or migration — start the service from the task branch and exercise the change with real requests, real logs and real DB side effects.
api-contract-testing
Use when a task adds or changes an HTTP endpoint, its request/response shape, status codes, auth or error format - the request matrix, curl templates and what counts as a contract break.
response-validation
Validate API response structure and content. Detects schema drift, unexpected null values, and abnormal response sizes.
api-tester
API testing expert for curl, REST, GraphQL, authentication, and debugging.