diff --git a/core/lib/Drupal/Core/Entity/EntityTypeManager.php b/core/lib/Drupal/Core/Entity/EntityTypeManager.php
index ab7f645..abe96a5 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeManager.php
@@ -17,13 +17,21 @@
 /**
  * Manages entity type plugin definitions.
  *
- * Each entity type definition array is set in the entity type's
- * annotation and altered by hook_entity_type_alter().
+ * Each entity type definition array is set in the entity type's annotation and
+ * altered by hook_entity_type_alter().
+ *
+ * Do not use hook_entity_type_alter() hook to add information to entity types,
+ * unless one of the following is true:
+ * - You are filling in default values.
+ * - You need to dynamically add information only in certain circumstances.
+ * - Your hook needs to run after hook_entity_type_build() implementations.
+ * Use hook_entity_type_build() instead in all other cases.
  *
  * @see \Drupal\Core\Entity\Annotation\EntityType
  * @see \Drupal\Core\Entity\EntityInterface
  * @see \Drupal\Core\Entity\EntityTypeInterface
  * @see hook_entity_type_alter()
+ * @see hook_entity_type_build()
  */
 class EntityTypeManager extends DefaultPluginManager implements EntityTypeManagerInterface, ContainerAwareInterface {