quicktype

quicktype infers types from sample JSON and generates models, serializers and validators in many programming languages. It is open source and can be used in the browser, from the command line or inside a build pipeline.

You give quicktype some JSON, a JSON Schema or a GraphQL query, and it produces code in the language you choose. Nested objects become named types, and the tool handles details such as nullable fields, enums, dates and unions. The output can include runtime checks that validate data as your program reads it, which helps catch unexpected shapes in API responses.

• Generate types from JSON, JSON Schema or GraphQL
• Output for more than 25 programming languages
• Create serializers and runtime validators
• Use it in the browser or on the command line
• Works inside build pipelines

Developers who work with API responses or large data files and want typed code without writing it by hand. Teams that share data models across several languages will also find it useful.

quicktype is open source under the Apache-2.0 licence and free to use. The project has more than 200 contributors, according to its page. Generated code is only as accurate as the sample data you give it, so review the output before you ship it. The page also mentions an MCP option for connecting coding tools.