API Contract Lab

Contract-first development made simple. Paste an OpenAPI spec, JSON example, or endpoint list — get mock responses, code snippets, and exportable Postman collections in seconds.

Multiple Input Formats

OpenAPI YAML/JSON, raw JSON examples, or simple endpoint lists. Paste what you have and we'll parse it.

Mock Response Generation

Realistic data per endpoint with status code variants — Success (200/201), Error (400/401/404), Server Error (500).

Code Snippets

Generate fetch, curl, Python requests, and React Query snippets ready to drop into your project.

Export Formats

Postman Collection v2.1, OpenAPI example bundle, and mock handler scripts for Express.js or FastAPI.

How It Works

Paste

Drop your OpenAPI spec, JSON sample, or endpoint list into the editor.

Parse

We extract paths, methods, schemas, and infer structure from your input.

Export

Get mock responses, code snippets, Postman collections, or mock server code.

Launch Tool
Build a UI for your API with PromptUI →