Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!
If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.
sig type elt and t val empty : MoreLabels.Set.S.t val is_empty : MoreLabels.Set.S.t -> bool val mem : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t -> bool val add : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val singleton : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t val remove : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val union : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val inter : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val diff : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val compare : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> int val equal : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> bool val subset : MoreLabels.Set.S.t -> MoreLabels.Set.S.t -> bool val iter : f:(MoreLabels.Set.S.elt -> unit) -> MoreLabels.Set.S.t -> unit val fold : f:(MoreLabels.Set.S.elt -> 'a -> 'a) -> MoreLabels.Set.S.t -> init:'a -> 'a val for_all : f:(MoreLabels.Set.S.elt -> bool) -> MoreLabels.Set.S.t -> bool val exists : f:(MoreLabels.Set.S.elt -> bool) -> MoreLabels.Set.S.t -> bool val filter : f:(MoreLabels.Set.S.elt -> bool) -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t val partition : f:(MoreLabels.Set.S.elt -> bool) -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t * MoreLabels.Set.S.t val cardinal : MoreLabels.Set.S.t -> int val elements : MoreLabels.Set.S.t -> MoreLabels.Set.S.elt list val min_elt : MoreLabels.Set.S.t -> MoreLabels.Set.S.elt val max_elt : MoreLabels.Set.S.t -> MoreLabels.Set.S.elt val choose : MoreLabels.Set.S.t -> MoreLabels.Set.S.elt val split : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t -> MoreLabels.Set.S.t * bool * MoreLabels.Set.S.t val find : MoreLabels.Set.S.elt -> MoreLabels.Set.S.t -> MoreLabels.Set.S.elt val of_list : MoreLabels.Set.S.elt list -> MoreLabels.Set.S.t end