TypeScript Type Generator

Generate TypeScript types and interfaces from JSON data, API responses, or plain English descriptions.

Use this prompt — free See example output

The Prompt

(2 messages)

System

You are a TypeScript expert. Generate precise, well-structured type definitions from the provided input.

Guidelines:
- Prefer interfaces for object shapes that may be extended; use type aliases for unions, intersections, and mapped types
- Use readonly for fields that shouldn't be mutated
- Use string literal unions instead of plain string where the values are known
- Add JSDoc comments on non-obvious fields
- Infer optional fields (?) when values could be null or absent
- Use utility types (Pick, Omit, Partial, Required) to reduce duplication
- Generate related types (e.g., CreateInput, UpdateInput) when useful

User

Generate TypeScript types from this input:

Input type: {{input_type}}

Input:
{{input}}

Variables

Fill in these inputs to customize your output:

{{input_type}}

Example: JSON API response

{{input}}

Example: { "id": "inv_28hd93", "status": "paid", "customer": { "id": "cust_19x8", "name": "Acme Corp", "email": "billing@acme.com" }, "line_items": [ { "description": "Pro Plan - Monthly", "quantity": 1, "unit_price": 4900, "amount": 4900 }, { "description": "Additional seats (3)", "quantity": 3, "unit_price": 1200, "amount": 3600 } ], "subtotal": 8500, "tax": 0, "total": 8500, "currency": "usd", "created_at": "2026-01-15T10:30:00Z", "paid_at": "2026-01-15T10:31:12Z" }

Example Output

Here's what this prompt generates with the sample inputs:

Sample outputgpt-4.1

interface Customer {
  readonly id: string
  name: string
  email: string
}

interface LineItem {
  description: string
  quantity: number
  /** Price in cents */
  unit_price: number
  /** Total for this line (quantity × unit_price), in cents */
  amount: number
}

type InvoiceStatus = 'draft' | 'open' | 'paid' | 'void' | 'uncollectible'
type Currency = 'usd' | 'eur' | 'gbp'

interface Invoice {
  readonly id: string
  status: InvoiceStatus
  customer: Customer
  line_items: LineItem[]
  /** Amount in cents before tax */
  subtotal: number
  /** Tax amount in cents */
  tax: number
  /** Total amount in cents (subtotal + tax) */
  total: number
  currency: Currency
  created_at: string
  paid_at: string | null
}

/** Fields required when creating a new invoice */
type CreateInvoiceInput = Omit<Invoice, 'id' | 'status' | 'subtotal' | 'tax' | 'total' | 'created_at' | 'paid_at'>

/** Fields that can be updated on an existing invoice */
type UpdateInvoiceInput = Partial<Pick<Invoice, 'status' | 'line_items' | 'customer'>>