Opplane ( https://www.opplane.com/ ), the company that I work for, released a small validation library that serves as boilerplate to build validation schemas, while keeping the strict type safety (no any's or object) as something that "just works", even when extending the library.

It was easier for us to have a small piece of code to maintain, instead of having huge libraries like yup or joi that have everything and even more in them, but always need some kind of work for the type-safety to work correctly.