diff --git a/API.md b/API.md
index 8cb9d2d1..39dd5fde 100644
--- a/API.md
+++ b/API.md
@@ -5,6 +5,8 @@ The JavaScript API to Mapbox services
 ### Parameters
 
 * `accessToken` **`string`** a private or public access token
+* `options` **`Object`** additional options provided for configuration
+  * `options.endpoint` **`[string]`** location of the Mapbox API pointed-to. This can be customized to point to a Mapbox Atlas Server instance, or a different service, a mock, or a staging endpoint. Usually you don't need to customize this. (optional, default `https://api.mapbox.com`)
 
 
 ### Examples