Guide · Agent skill
How to use the API Mocking Framework agent skill
Updated · written with AI from the project's own documentation and checked against our catalogue data
The API Mocking Framework is an agent skill that tells your AI agent how to build realistic mock versions of an API, for development, integration testing or demos. After this guide you will know what the skill changes about the agent's behaviour, how to install it, how to phrase requests so it triggers, and what limits to respect.
API Mocking Frameworksickn33/agentic-awesome-skills · MIT Download the skill Quick start
- 1Download the ZIP. Download the skill ZIP from this page.
- 2Unzip into the skills folder. Unzip it into ~/.claude/skills/ for personal use, or into .claude/skills/ in your project.
- 3Or upload in the Claude apps. In the Claude apps, go to Settings → Capabilities → Skills and upload the skill.
- 4Describe the API you need. Explain which API you are mocking, its auth method, its endpoints and its error responses.
- 5Answer the contract questions. The agent will clarify the contract, auth flow, error shapes and latency before designing routes.
- 6Run and switch scenarios. Ask the agent to document how to start the mock server and switch between success, error and slow scenarios.
What is an agent skill and what does this one make the agent do?
An agent skill is a folder containing a SKILL.md file with instructions that an AI agent loads when a request matches the skill's description. This skill's description says the agent acts as an API mocking expert for development, testing and demos, designing mocks that simulate real API behaviour so teams can work in parallel.
When the skill is active, the agent first clarifies the API contract, auth flows, error shapes and latency expectations. It then plans routes, scenarios and state transitions before writing responses. The skill aims for deterministic fixtures with optional randomness, and asks the agent to document how to run the mock server and switch between scenarios.
Install the skill from the ZIP or the Claude apps
Download the ZIP for this skill from this page and unzip it into one of two places. For a personal setup, use ~/.claude/skills/. For a single project, use the .claude/skills/ folder inside that project.
If you use the Claude apps instead, open Settings, go to Capabilities, and upload the skill under Skills.
- Personal: unzip into ~/.claude/skills/
- Project only: unzip into .claude/skills/ in your project root
- Claude apps: Settings → Capabilities → Skills, then upload
Trigger the skill with natural requests
You do not need a special command. Describe the mock you want in plain language that matches the skill's purpose: an API that does not exist yet, a partner API to simulate, or a demo sandbox. Including the endpoints, auth method and error responses you expect helps the agent clarify the contract faster.
The skill's own guidance says it should only be used when the task clearly matches its scope. If your request is about testing a live system, expect the agent to decline that part.
- Build a mock of the orders API so the frontend team can start before the backend is done.
- Simulate our payments partner's API for integration tests, including 401 and 503 responses.
- Create a safe demo sandbox API for the sales team with three scenarios: success, slow and unavailable.
What the agent will ask you before writing mocks
Expect questions about the contract, the auth flow, the shape of error responses and how long responses should take. The skill tells the agent to stop and ask when required inputs, permissions or success criteria are missing, so answering these up front gives better output.
- The endpoints, methods and request/response shapes to mirror
- How authentication works (for example, a token header)
- The error bodies and status codes the real API returns
- Expected latency, and which scenarios should be slow or fail
- Which scenarios the team needs to switch between
Use the implementation playbook for code details
The skill includes resources/implementation-playbook.md, which holds code samples, checklists and templates. The agent opens it when you ask for detailed implementation. The playbook includes a standard-library Python fixture resolver that maps a method, path and scenario to a fixed response and returns a copy so one test cannot change another's data.
Be aware that the playbook's larger server classes are design sketches. They depend on helper modules that are not included, so they are not a runnable mock framework. Use an existing project mocking library, or implement and test the missing parts yourself.
FIXTURES = {("GET", "/users/example", "success"): {"status": 200, "body": {"id": "example"}}}Safety: scripts, network and data
This skill lists no required tools, runs no scripts and makes no network calls. Its instructions say to avoid reusing production secrets or real customer data in mocks, and to label mock endpoints clearly so they are not mistaken for live services.
The skill is not for testing production or live integrations, and it excludes security or penetration testing. A mock cannot prove that a real integration works, so validate against the real provider separately.
- Do not paste production API keys or customer records into prompts or fixtures
- Label mock hosts and responses so they cannot be confused with live endpoints
- Treat the output as a starting point, not a substitute for expert review
What people use it for
- Frontend developers building screens against an API the backend team has not finished.
- Integration test suites that need a stable stand-in for a partner or third-party API.
- Sales or demo teams who need a realistic sandbox that is safe to show customers.
- Designing and checking an API contract before any backend code exists.
Frequently asked questions
How do I install the API Mocking Framework agent skill?
Download the ZIP from this page and unzip it into ~/.claude/skills/ for personal use, or into .claude/skills/ inside a project. You can also upload it in the Claude apps under Settings → Capabilities → Skills.
Does this skill need any requirements or tools installed?
The skill lists no required dependencies, runs no scripts and uses no network access. The playbook's Python example uses only the standard library.
Is the API Mocking Framework skill free?
The skill is published under the MIT licence, as stated on this page. Check the licence file in the repository for the full terms.
Can I use this skill to test a live or production API?
No. The skill says not to test production systems or live integrations, because mocks do not validate real integrations. Use it for development, integration tests against simulated partners, and demos.
What is the difference between this skill and a mock server library?
The skill guides the agent in designing routes, scenarios, fixtures and documentation. It does not replace a mocking library: the playbook says to use an existing project-local library or implement and test the dependencies yourself.
Why does the generated mock server code not run?
The playbook's larger server classes depend on route, state, scenario and validation helpers that are not included. They are design material, so you need to implement and test those helpers before the code can run.
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Our verdict
Use this skill if you are a frontend developer waiting on an API, a team writing integration tests against a partner API, or a demo team that needs a safe sandbox. Pick something else if you need to test live or production systems, run security testing, or have no API contract to mirror, since the mock would be guesswork.
Download the skill