diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
index 5aa737d..d55e670 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
@@ -18,7 +18,7 @@
    * Returns the original ID.
    *
    * @return string|null
-   *   The original ID, if any.
+   *   The original ID, or NULL if no ID was set.
    */
   public function getOriginalId();
 
@@ -28,23 +28,21 @@ public function getOriginalId();
    * @param string $id
    *   The new ID to set as original ID.
    *
-   * @return self
+   * @return $this
    */
   public function setOriginalId($id);
 
   /**
    * Enables the configuration entity.
    *
-   * @return \Drupal\Core\Config\Entity\ConfigEntityInterface
-   *   The configuration entity.
+   * @return $this
    */
   public function enable();
 
   /**
    * Disables the configuration entity.
    *
-   * @return \Drupal\Core\Config\Entity\ConfigEntityInterface
-   *   The configuration entity.
+   * @return $this
    */
   public function disable();
 
@@ -54,8 +52,7 @@ public function disable();
    * @param bool $status
    *   The status of the configuration entity.
    *
-   * @return \Drupal\Core\Config\Entity\ConfigEntityInterface
-   *   The class instance that this method is called on.
+   * @return $this
    */
   public function setStatus($status);
 
@@ -80,14 +77,41 @@ public function setSyncing($status);
    *     checking and managing the status.
    *
    * @return bool
+   *   Whether the entity is enabled or not.
    */
   public function status();
 
   /**
-   * Returns whether the configuration entity is created, updated or deleted
-   * through the import process.
+   * Returns whether this entity is being changed as part of an import process.
+   *
+   * Code that makes changes to configuration or the entities that are being
+   * changed, but not imported entities that may already contain
+   * these changes, must check this method.
+   *
+   * If you are writing code that responds to a change in this entity (insert,
+   * update, delete, presave, etc.), and your code would result in a
+   * configuration change (whether related to this configuration entity, another
+   * configuration entity, or non-entity configuration) or your code would
+   * result in a change to this entity itself, you need to check and see if this
+   * entity change is part of an import process, and skip executing your code if
+   * that is the case.
+   *
+   * For example, \Drupal\node\Entity\NodeType::postSave() adds the default body
+   * field to newly created node type configuration entities, which is a
+   * configuration change. You would not want this code to run during an import,
+   * because imported entities were already given the body field when they were
+   * originally created, and the imported configuration includes all of their
+   * currently-configured fields. On the other hand,
+   * \Drupal\field\Entity\Field::preSave() and the methods it calls make sure
+   * that the storage tables are created or updated for the field configuration
+   * entity, which is not a configuration change, and it must be done whether
+   * due to an import or not. So, the first method should check
+   * $entity->isSynching() and skip executing if it returns TRUE, and the second
+   * should not perform this check.
    *
    * @return bool
+   *   TRUE if the configuration entity is being created, updated, or deleted
+   *   through the import process.
    */
   public function isSyncing();
 
@@ -98,7 +122,7 @@ public function isSyncing();
    *   The name of the property that should be returned.
    *
    * @return mixed
-   *   The property, if existing, NULL otherwise.
+   *   The property if it exists, or NULL otherwise.
    */
   public function get($property_name);
 
@@ -117,7 +141,7 @@ public function set($property_name, $value);
    *
    * These are the values that get saved into config.
    *
-   * @return array
+   * @return mixed[]
    *   An array of exportable properties and their values.
    */
   public function getExportProperties();
diff --git a/core/lib/Drupal/Core/Entity/EntityInterface.php b/core/lib/Drupal/Core/Entity/EntityInterface.php
index 057727b..eb2065f 100644
--- a/core/lib/Drupal/Core/Entity/EntityInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityInterface.php
@@ -224,7 +224,7 @@ public function postSave(EntityStorageControllerInterface $storage_controller, $
    *
    * @param \Drupal\Core\Entity\EntityStorageControllerInterface $storage_controller
    *   The entity storage controller object.
-   * @param array $values
+   * @param mixed[] $values
    *   An array of values to set, keyed by property name. If the entity type has
    *   bundles the bundle key has to be specified.
    */
@@ -233,7 +233,7 @@ public static function preCreate(EntityStorageControllerInterface $storage_contr
   /**
    * Acts on an entity after it is created but before hooks are invoked.
    *
-   * @param EntityStorageControllerInterface $storage_controller
+   * @param \Drupal\Core\Entity\EntityStorageControllerInterface $storage_controller
    *   The entity storage controller object.
    */
   public function postCreate(EntityStorageControllerInterface $storage_controller);
@@ -245,7 +245,7 @@ public function postCreate(EntityStorageControllerInterface $storage_controller)
    *
    * @param EntityStorageControllerInterface $storage_controller
    *   The entity storage controller object.
-   * @param \Drupal\Core\Entity\EntityInterface[] $entities
+   * @param static[] $entities
    *   An array of entities.
    */
   public static function preDelete(EntityStorageControllerInterface $storage_controller, array $entities);
@@ -257,7 +257,7 @@ public static function preDelete(EntityStorageControllerInterface $storage_contr
    *
    * @param EntityStorageControllerInterface $storage_controller
    *   The entity storage controller object.
-   * @param \Drupal\Core\Entity\EntityInterface[] $entities
+   * @param static[] $entities
    *   An array of entities.
    */
   public static function postDelete(EntityStorageControllerInterface $storage_controller, array $entities);
@@ -267,7 +267,7 @@ public static function postDelete(EntityStorageControllerInterface $storage_cont
    *
    * @param EntityStorageControllerInterface $storage_controller
    *   The entity storage controller object.
-   * @param \Drupal\Core\Entity\EntityInterface[] $entities
+   * @param static[] $entities
    *   An array of entities.
    */
   public static function postLoad(EntityStorageControllerInterface $storage_controller, array &$entities);
@@ -285,7 +285,7 @@ public function createDuplicate();
    * Returns the entity type definition.
    *
    * @return \Drupal\Core\Entity\EntityTypeInterface
-   *   Entity type definition.
+   *   The entity type definition.
    */
   public function getEntityType();