diff --git a/core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php
index aa917c845c..eef908d749 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php
@@ -19,7 +19,10 @@ class EntityTypeBundleInfo implements EntityTypeBundleInfoInterface {
   /**
    * Static cache of bundle information.
    *
-   * @var array
+   * The array has the same structure as the return value of
+   * \Drupal\Core\Entity\EntityTypeBundleInfoInterface::getAllBundleInfo().
+   *
+   * @var array[]
    */
   protected $bundleInfo;
 
diff --git a/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
index 2789b651e5..88e56dd275 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
@@ -10,11 +10,13 @@
   /**
    * Get the bundle info of all entity types.
    *
-   * @return array
-   *   An array of bundle information where the outer array is keyed by entity
-   *   type. The next level is keyed by the bundle name. The inner arrays are
-   *   associative arrays of bundle information, such as the label for the
-   *   bundle.
+   * @return array[]
+   *   An array of all bundle information, whose keys are entity type IDs and
+   *   values are (second-level) arrays whose keys are bundle names, and
+   *   values are (third-level) arrays with the same structure as the return
+   *   value of static::getBundleInfo().
+   *
+   * @see static::getBundleInfo()
    */
   public function getAllBundleInfo();
 
@@ -24,11 +26,16 @@ public function getAllBundleInfo();
    * @param string $entity_type_id
    *   The entity type ID.
    *
-   * @return array
-   *   An array of bundle information where the outer array is keyed by the
-   *   bundle name, or the entity type name if the entity does not have bundles.
-   *   The inner arrays are associative arrays of bundle information, such as
-   *   the label for the bundle.
+   * @return mixed[]
+   *   An array of bundle information whose keys are bundle names and values
+   *   are (second-level) arrays with the following keys:
+   *   - label: The human-readable name of the bundle.
+   *   - uri_callback: The same as the 'uri_callback' key defined for the entity
+   *     type in its definition, but for the bundle only. When determining the
+   *     URI of an entity, if a 'uri_callback' is defined for both the entity
+   *     type and the bundle, the one for the bundle is used.
+   *   - translatable: (optional) TRUE if the bundle has translation support,
+   *     FALSE (default) if not.
    */
   public function getBundleInfo($entity_type_id);
 
diff --git a/core/lib/Drupal/Core/Entity/entity.api.php b/core/lib/Drupal/Core/Entity/entity.api.php
index f31561d70c..fb1adbc27a 100644
--- a/core/lib/Drupal/Core/Entity/entity.api.php
+++ b/core/lib/Drupal/Core/Entity/entity.api.php
@@ -836,16 +836,10 @@ function hook_entity_view_mode_info_alter(&$view_modes) {
 /**
  * Describe the bundles for entity types.
  *
- * @return array
- *   An associative array of all entity bundles, keyed by the entity
- *   type name, and then the bundle name, with the following keys:
- *   - label: The human-readable name of the bundle.
- *   - uri_callback: (optional) The same as the 'uri_callback' key defined for
- *     the entity type in the EntityTypeManager, but for the bundle only. When
- *     determining the URI of an entity, if a 'uri_callback' is defined for both
- *     the entity type and the bundle, the one for the bundle is used.
- *   - translatable: (optional) A boolean value specifying whether this bundle
- *     has translation support enabled. Defaults to FALSE.
+ * @return array[]
+ *   An array of all bundle information with the same structure as the return
+ *   value of
+ *   \Drupal\Core\Entity\EntityTypeBundleInfoInterface::getAllBundleInfo().
  *
  * @see \Drupal\Core\Entity\EntityTypeBundleInfo::getBundleInfo()
  * @see hook_entity_bundle_info_alter()
@@ -858,8 +852,10 @@ function hook_entity_bundle_info() {
 /**
  * Alter the bundles for entity types.
  *
- * @param array $bundles
- *   An array of bundles, keyed first by entity type, then by bundle name.
+ * @param array[] $bundles
+ *   An array of all bundle information with the same structure as the return
+ *   value of
+ *   \Drupal\Core\Entity\EntityTypeBundleInfoInterface::getAllBundleInfo().
  *
  * @see Drupal\Core\Entity\EntityTypeBundleInfo::getBundleInfo()
  * @see hook_entity_bundle_info()