Validation & schemas

Every tool carries a Zod schema, so one definition gives you runtime validation, static types, and a JSON-Schema description. TypeScript can’t catch a negative age at a form boundary; the schema can:

import { REGISTRY } from "@almostjacked/fitness-tools";
const tdee = REGISTRY.get("tdee")!;
const r = tdee.input.safeParse({ sex: "male", age: -5 /* … */ });
if (!r.success) {
  // r.error.issues → per-field errors you can render in a form
}

The same schemas are what generate the HTTP API catalog and OpenAPI spec — no hand-written API docs.