FromJson Desk — a JSON payload in, a Dart model that decodes it out

Paste a JSON payload your Flutter or Dart app receives. Free in your browser: it is read the way Dart's jsonDecode reads it (int versus double, missing and null keys), a null-safe dart:convert model with fromJson and toJson is generated, and the model you already have is run against every sample to show which cast throws and why. Then a review explains each failure with the corrected Dart, or a write produces the model file, its unit test and its fetch function, and the page runs the written model against your samples again. Derived from the agent skill @flutter/flutter-implement-json-serialization (flutter/skills, BSD-3-Clause).

Every public app is built from a security-scanned skill and must pass a clean scan — skill and frontend — before it can be listed. Have a skill of your own? Turn it into an app — or read the step-by-step walkthrough.