JSON to TypeScript Interface Generator

Why generate TypeScript from JSON?

• API response typing: receive JSON from a backend → auto-generate types for the frontend, no manual typing.
• LLM structured output: Claude / OpenAI / Gemini all support structured output by schema. Design a JSON sample, use this tool to get TS, then validate with Zod or Valibot.
• Mock data: have fake data → generate an interface to type-check your tests.
• Refactor: legacy JS codebase → migrate to TS, paste a JSON sample to get the interface instantly.

Features

• Nested types split out: JSON with sub-objects → the tool generates a separate interface per level.
• Inline mode: keep everything in one interface — toggle the option.
• Array → homogeneous type: ["a","b"] → string[]. Mixed → Array<string | number>.
• readonly / optional: apply to all fields — useful for immutable API responses or form inputs.
• export keyword: paste straight into a .ts file.

Real-world example with the Claude API

Want Claude to return a structured response? Start with a JSON sample:

{
  "summary": "An article about AI",
  "topics": ["LLM", "RAG"],
  "sentiment": "positive",
  "actionItems": [
    { "task": "read more", "priority": "high" }
  ]
}

The tool generates:

export interface ActionItem {
  task: string;
  priority: string;
}

export interface Root {
  summary: string;
  topics: string[];
  sentiment: string;
  actionItems: ActionItem[];
}

Use with Zod to validate the response:

import { z } from 'zod';

const ActionItemSchema = z.object({
  task: z.string(),
  priority: z.string(),
});
const RootSchema = z.object({
  summary: z.string(),
  topics: z.array(z.string()),
  sentiment: z.string(),
  actionItems: z.array(ActionItemSchema),
});