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.
module Asttypes: sig .. endtype constant = | | | Const_int of int | 
| | | Const_char of char | 
| | | Const_string of string * string option | 
| | | Const_float of string | 
| | | Const_int32 of int32 | 
| | | Const_int64 of int64 | 
| | | Const_nativeint of nativeint | 
type rec_flag = | | | Nonrecursive | 
| | | Recursive | 
type direction_flag = | | | Upto | 
| | | Downto | 
type private_flag = | | | Private | 
| | | Public | 
type mutable_flag = | | | Immutable | 
| | | Mutable | 
type virtual_flag = | | | Virtual | 
| | | Concrete | 
type override_flag = | | | Override | 
| | | Fresh | 
type closed_flag = | | | Closed | 
| | | Open | 
type label = string 
type 'a loc = 'a Location.loc = {|    | txt : 'a; | 
|    | loc : Location.t; | 
type variance = | | | Covariant | 
| | | Contravariant | 
| | | Invariant |