Quickstart: Write a typed client in TypeScript

Model the responses

interface Product {
  id: string;
  name: string;
  type: 'flex' | 'onetime';
  min_amount: number;
  max_amount: number;
  representative_apr: number;
}
interface ApiError {
  error: { type: string; code: string; message: string; request_id: string };
}
async function listProducts(base: string): Promise<Product[]> {
  const res = await fetch(`${base}/products`);
  const body = await res.json();
  if (!res.ok) throw new Error((body as ApiError).error.code);
  return (body as { data: Product[] }).data;
}

Generate types from the schema

If you consume many endpoints, generate types from the published OpenAPI description rather than hand-writing them, so your client stays in lockstep with the API contract.