diff --git modules/system/system.api.php modules/system/system.api.php
index c68d893..6eefe43 100644
--- modules/system/system.api.php
+++ modules/system/system.api.php
@@ -67,6 +67,9 @@ function hook_hook_info_alter(&$hooks) {
  * can be loaded via entity_load() and, optionally, to which fields can be
  * attached).
  *
+ * Note: It is recommended to have a save function per entity type
+ * that takes an entity object and saves it into the database.
+ *
  * @return
  *   An array whose keys are entity type names and whose values identify
  *   properties of those types that the system needs to know about: