I ran one API response through two JSON-to-Zod converters. One silently turned every field into z.string().

You have an API response. You want a Zod schema. So you paste the JSON into a JSON-to-Zod converter, copy the output, and ship it. Here's the trap: a lot of those converters infer basic types only . Your email , your uuid , your url , your ISO timestamp — they all come out as z.string() . The schema compiles, the types look right, and your validator quietly accepts "not-an-email" , "ftp://nope" , and "2026-99-99" forever. I wanted to see exactly how much gets lost, so I ran the same payload through two tools and diffed the output. Everything below is real, copy-pasteable output — nothing edited. The input A pretty ordinary user object: { "id" : "3f2a9c1e-5b7d-4e8a-9f1c-2d3e4f5a6b7c" , "email" : "ada@example.com" , "website" : "https://ada.dev" , "age" : 34 , "rating" : 4.7 , "created_at" : "2026-03-04T10:15:30Z" , "is_active" : true , "address" : { "city" : "Lyon" , "zip" : "69001" }, "tags" : [ "early-adopter" , "beta" ] } Tool 1 — json-to-zod (npm) const user = z . object ({ id : z . string (), email : z . string (), website : z . string (), age : z . number (), rating : z . number (), created_at : z . string (), is_active : z . boolean (), address : z . object ({ city : z . string (), zip : z . string () }), tags : z . array ( z . string ()), }); Structurally correct. But every meaningful field is a bare z.string() / z.number() . This schema will happily validate email: "lol" and created_at: "yesterday" . Tool 2 — TypeMorph import { z } from " zod " ; export const userAddressSchema = z . object ({ city : z . string (), zip : z . string (). regex ( /^ [ A-Z0-9 ][ A-Z0-9 \s\-]{1,8}[ A-Z0-9 ] $/i ), }); export type UserAddress = z . infer < typeof userAddressSchema > ; export const userSchema = z . object ({ id : z . uuid (), email : z . email (), website : z . url (), age : z . number (). int (). min ( 0 ). max ( 150 ), rating : z . number (). min ( 0 ). max ( 5 ), created_at : z . iso . datetime (), is_active : z . boolean (), address : userAddressSchema , tags :