JSON to C#, Java, Python, and TypeScript Class Generator

Convert a JSON sample into model classes or TypeScript interfaces for several programming languages.

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// about

About this Tool

This tool infers a model structure from a JSON sample and generates starter code. Review optional fields, nested objects, names, and data types before using the result.

How to use it

  1. Paste a representative JSON object or array.
  2. Choose a target language and enter the root class name.
  3. Click Generate, review inferred types, then copy and adapt the code.

Why people use this tool

  • Turn a JSON API response into starter model code quickly.
  • Generate code for C#, Java, Python, JavaScript, or TypeScript.
  • Inspect nested objects and arrays before integrating the generated model.

Frequently Asked Questions

Is the generated model production-ready?

It is a starting point. Validate optional fields, dates, nullability, and nested data against your API contract.

Guides · Data · 7 min read

Fixing JSON Syntax Errors: The 7 Most Common Mistakes and How to Clean Up JSON

API responses, configuration files and logs: JSON is the data format developers read most. Yet a single comma or quote can trigger an 'Unexpected token' error. Here is how to find the cause quickly.

JSON (JavaScript Object Notation) is a text format standardised in RFC 8259 and ECMA-404. It came from JavaScript but is now supported by almost every language. There are only six value types: string, number, boolean (true/false), null, array and object.

{
  "id": 1024,
  "name": "AIBIZAP",
  "active": true,
  "tags": ["tools", "guides"],
  "owner": null
}
JSON basics, seven mistakes that cause parse errors, pitfalls with big numbers and dates, and how to turn JSON into classes or database tables.
Read guide →
Build it with AI

Build this tool yourself with AI

Want your own version of this tool? Copy the work-order prompt into an AI chat, or save the skill file for an AI coding agent. Both describe the features, edge cases and test cases we used when building it.

AI work-order prompt

Paste it as-is into an AI chat such as Claude, ChatGPT or Gemini.

You are an experienced full-stack web developer. Build a web tool called "JSON to Class Generator" that meets the requirements below.

## Goal

Build a tool that generates C#, Java, Python and TypeScript model classes from a JSON sample.

## Core features

- Choose C#, Java, Python dataclasses or TypeScript interfaces
- Create separate classes for nested objects
- Infer array element types
- Set the root class name
- Apply each language's naming conventions

## Inputs

- JSON sample
- Target language and root class name

## Outputs

- Generated code
- Summary of inferred types

## Edge cases and handling rules

- Treat null values as nullable types
- Merge differing keys across array elements
- Handle keys that clash with reserved words
- Keep original names for keys with digits or hyphens via serialization attributes

## Implementation requirements

- Build it as a single page (HTML, CSS, JavaScript) that runs entirely in the browser, and never send the user's input to a server.
- Make the UI responsive and easy to use on mobile; label every input and keep everything keyboard accessible.
- Add a Copy button for results and show clear, friendly error messages for invalid input.
- Keep the core logic in functions separate from the UI so it can be unit-tested.

## Definition of done (test cases)

- {"id":1,"name":"a"} gives int Id and string Name in C#
- Nested objects become separate classes
- Empty arrays become lists of object/any

First outline your implementation plan in at most five lines, then write the complete code, and finally explain how to check the test cases above.

Skill (SKILL.md)

Save it as .claude/skills/build-json-class-generator/SKILL.md for AI coding agents such as Claude Code to reuse whenever you build or change this tool.

---
name: build-json-class-generator
description: Use when building or changing a JSON to Class Generator tool. Build a tool that generates C#, Java, Python and TypeScript model classes from a JSON sample.
---

# Build: JSON to Class Generator

## Goal

Build a tool that generates C#, Java, Python and TypeScript model classes from a JSON sample.

## Workflow

1. Review the required features, inputs and outputs below and ask about anything missing first.
2. Implement the core logic as pure functions separate from the UI.
3. Check the logic against the test cases in the verification list.
4. Build a responsive UI with an input form, a result area and a Copy button.
5. Reproduce each edge case listed under Rules and refine the error messages.

## Core features

- Choose C#, Java, Python dataclasses or TypeScript interfaces
- Create separate classes for nested objects
- Infer array element types
- Set the root class name
- Apply each language's naming conventions

## Inputs

- JSON sample
- Target language and root class name

## Outputs

- Generated code
- Summary of inferred types

## Rules

- Treat null values as nullable types
- Merge differing keys across array elements
- Handle keys that clash with reserved words
- Keep original names for keys with digits or hyphens via serialization attributes
- Build it as a single page (HTML, CSS, JavaScript) that runs entirely in the browser, and never send the user's input to a server.

## Verification

- [ ] {"id":1,"name":"a"} gives int Id and string Name in C#
- [ ] Nested objects become separate classes
- [ ] Empty arrays become lists of object/any

Tips for working with AI

  • Tell the AI your stack (for example React, Vue or plain HTML) on the first line so the code matches your project.
  • Ask it to run the listed test cases and show the results before you accept the code.
  • Never paste real secrets, customer data or API keys into the prompt; use sample values instead.