Why convert JSON to GraphQL?

When migrating from REST to GraphQL or wrapping existing REST APIs with a GraphQL layer, you need schema definitions that match your existing data shapes. Manually writing type definitions for complex nested JSON responses is tedious and error-prone. This tool automates the process by analyzing your JSON structure and generating accurate GraphQL types with proper scalar assignments.

// Generate GraphQL schema from API response

// API response JSON:
// { "users": [{ "id": "u1", "name": "Alice", "posts": [{ "title": "Hello" }] }] }

// Generated GraphQL schema:
type Query {
  users: [User!]!
}

type User {
  id: ID!
  name: String!
  posts: [Post!]!
}

type Post {
  title: String!
}

// JavaScript — infer types from JSON
function jsonToGraphQLType(obj) {
  if (typeof obj === "string") return "String";
  if (typeof obj === "number") return Number.isInteger(obj) ? "Int" : "Float";
  if (typeof obj === "boolean") return "Boolean";
  return "String";
}

How type inference works

The generator analyzes each JSON value to determine its GraphQL scalar type: strings become String, integers become Int, floats become Float, booleans become Boolean. Fields named 'id' or ending in '_id' are mapped to the ID scalar. ISO date strings are detected and mapped to custom DateTime or Date scalars. Nested objects become separate GraphQL types, and arrays become list types.