Programmatic Schemas with TypeBox

Building Schemas Programmatically with TypeBox

Instead of using JSON Schemas, you have the option to define your schemas using TypeBox.


import { createRouter, Response, Type } from 'fets'
const router = createRouter().route({
  path: '/user/:id',
  method: 'POST',
  schemas: {
    request: {
      headers: Type.Object({
        authorization: Type.String().regex(/Bearer .+/)
      params: Type.Object({
        id: Type.String({
          format: 'uuid'
  // Response type will be automatically inferred from the handler's return type
  handler: request => {
    if ( !== EXPECTED_UUID) {
      return Response.json(
          message: 'User not found'
          status: 404
    return Response.json({
      name: 'John Doe'

Why not Zod?

feTS uses JSON Schemas, and libraries like Zod have their own API and logic to handle validations and modeling. With feTS, you can use any tool that generates JSON Schemas programmatically but we recommend using TypeBox which keeps the types of output JSON Schemas so feTS can infer types from them. And without any conversion process, those generated schemas can be directly added into the OpenAPI document.

In addition, you can see how fast TypeBox is; Type Benchmarks