Api mock

Skill kasimmj/claude-skills-mega/skills/api-mock

Generate a working mock server from an OpenAPI/Swagger spec or from a verbal API description. Outputs Express (Node), FastAPI (Python), or Hono (TypeScript).From its SKILL.md

Install

npx -y skills add kasimmj/claude-skills-mega --skill api-mock

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SKILL.md

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API Mock Skill

You are generating a mock HTTP server. The output should be a runnable file that any developer can npm start or python main.py to test against.

Step 1 — Identify the source

Look for, in order:

An OpenAPI/Swagger file (openapi.yaml, swagger.json)
A REST description in the user's message
A routes.md / API.md in the repo

If unclear, ask for the API shape.

Step 2 — Pick the framework

Detect from existing project files:

package.json with Express/Fastify/Hono → match it
requirements.txt with FastAPI/Flask → match it
Otherwise: default to Hono (smallest, runs anywhere, TypeScript native)

Step 3 — Generate the mock

For each endpoint:

Return realistic mock data using faker (Node) or Faker (Python)
Honor status codes — if the spec says 201, return 201
Add Content-Type headers
Add a 200–800ms artificial latency (configurable)
Support pagination: ?limit=N&page=N

For errors:

/error/500 — always returns 500
/error/timeout — never responds
/error/slow — 10s delay
These help frontend devs test error states.

Step 4 — Add CORS

Always enable CORS with Access-Control-Allow-Origin: * for the mock. It's a dev tool — security doesn't apply.

Step 5 — Output

A single file with:

All routes
Faker setup with a fixed seed (reproducible data)
Healthcheck at GET /health
An if __name__ or app.listen() block
A header comment with the run command

When NOT to use

The user wants a real API — use api-build skill instead
The user wants contract tests — use contract-test skill

Failure modes

⚠️ Don't add auth to the mock unless asked. Defeats the purpose.
⚠️ If the spec is huge (>50 endpoints), generate the highest-traffic 10 and ask before generating the rest.

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.