diff --git a/src/Visibility.js b/src/Visibility.js
index a0cb07d..05b5903 100644
--- a/src/Visibility.js
+++ b/src/Visibility.js
@@ -1,6 +1,12 @@
 import { Circle } from 'infinite-circle';
 import RouterEvents from 'ima/router/Events';
 
+/**
+ * @callback notifyCallback
+ * @param {Object} payload
+ * @param {string} payload.type
+ */
+
 /**
  * Visibility helper.
  */
@@ -112,6 +118,8 @@ export default class Visibility {
 
   /**
    * The visibility helper start checking visibility of registered entries.
+   *
+   * @param {notifyCallback}
    */
   _listenOnEvents(notify) {
     this._dispatcher.listen(RouterEvents.AFTER_HANDLE_ROUTE, notify);
@@ -121,6 +129,8 @@ export default class Visibility {
 
   /**
    * The visibility helper stop checking visibility of registered entries.
+   *
+   * @param {notifyCallback}
    */
   _unlistenOnEvents(notify) {
     this._dispatcher.unlisten(RouterEvents.AFTER_HANDLE_ROUTE, notify);