I totally agree with you here; statically typed languages (OMG OCaml) are great for making code very readable/documented, IMHO. I just have so much more confidence in my code when the compiler has my back.

Another commenter pointed this out, but Typed Racket is a Racket variant (which is a scheme-ish variant) that implements "gradual typing". I've played with it here and there and am about to dive in again.

https://docs.racket-lang.org/ts-guide/