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 val fprintf : Pervasives.out_channel -> ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a val printf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a val eprintf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a val sprintf : ('a, unit, string) Pervasives.format -> 'a val bprintf : Buffer.t -> ('a, Buffer.t, unit) Pervasives.format -> 'a val ifprintf : 'a -> ('b, 'a, unit) Pervasives.format -> 'b val kfprintf : (Pervasives.out_channel -> 'a) -> Pervasives.out_channel -> ('b, Pervasives.out_channel, unit, 'a) Pervasives.format4 -> 'b val ikfprintf : (Pervasives.out_channel -> 'a) -> Pervasives.out_channel -> ('b, Pervasives.out_channel, unit, 'a) Pervasives.format4 -> 'b val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b val kbprintf : (Buffer.t -> 'a) -> Buffer.t -> ('b, Buffer.t, unit, 'a) Pervasives.format4 -> 'b val kprintf : (string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b end