Send JSON and get a typed result back

Task

You are POSTing JSON to an API and want the result back as a typed value — and you would like bad input rejected before it leaves the process, not returned to you as a 400 from the server.

Example

One way: validate the body going out and the response coming back, and type the result with the stitch<T> generic.

import { stitch, toValidator } from 'stitchapi';
import { z } from 'zod';

const createUser = stitch<{ id: number; name: string }>({
    method: 'POST',
    baseUrl: 'https://api.example.com',
    path: '/users',
    input: { body: toValidator(z.object({ name: z.string() })) },
    output: toValidator(z.object({ id: z.number(), name: z.string() })),
});

// A bad body throws before the POST; a bad response throws after.
const user = await createUser({ body: { name: 'Ada' } });

user is typed { id: number; name: string }.

How it works

input.body is checked before the request — wrong input fails fast with no network call. output is checked after the response returns. Either failure throws STITCH_VALIDATION. The stitch<T> generic types the resolved value, and toValidator() adapts the Zod schema to the Validator the config expects — pass toValidator(z.object({...})), not a raw z.object({...}). Any Standard Schema validator (Valibot, ArkType) goes through the same toValidator() call.

See also