diff -u b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterKernelListenersPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterKernelListenersPass.php
--- b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterKernelListenersPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterKernelListenersPass.php
@@ -2,8 +2,7 @@
 
 /**
  * @file
- * Definition of
- * Drupal\Core\DependencyInjection\Compiler\RegisterKernelListenersPass.
+ * Contains Drupal\Core\DependencyInjection\Compiler\RegisterKernelListenersPass.
  */
 
 namespace Drupal\Core\DependencyInjection\Compiler;
diff -u b/core/lib/Drupal/Core/DependencyInjection/Compiler/StackedKernelPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/StackedKernelPass.php
--- b/core/lib/Drupal/Core/DependencyInjection/Compiler/StackedKernelPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/StackedKernelPass.php
@@ -13,6 +13,7 @@
 
 /**
  * Provides a compiler pass for stacked HTTP kernels.
+ *
  * @see \Stack\Builder
  *
  * @service_tag http_middleware
diff -u b/core/modules/serialization/src/RegisterSerializationClassesCompilerPass.php b/core/modules/serialization/src/RegisterSerializationClassesCompilerPass.php
--- b/core/modules/serialization/src/RegisterSerializationClassesCompilerPass.php
+++ b/core/modules/serialization/src/RegisterSerializationClassesCompilerPass.php
@@ -15,14 +15,24 @@
  * Adds services tagged 'normalizer' and 'encoder' to the Serializer.
  *
  * @service_tag encoder
- *   @todo  fill this in
+ *   Services that provide object serialization encoders must be tagged
+ *   'encoder' to be registered to the serializer service. Parameters are:
+ *   - format: The encoding format for this encoder. Example: json.
+ *   - priority: (optional) An integer priority for this encoder. The default
+ *       priority is 0.
  *   This tag is processed by
  *   \Drupal\serialization\RegisterSerializationClassesCompilerPass.
  *
  * @service_tag normalizer
- *   @todo  fill this in
+ *   Services that provide object serialization normalizers must be tagged
+ *   'normalizer' to be registered to the serializer service. Parameters are:
+ *   - priority: (optional) An integer priority for this normalizer. The default
+ *       priority is 0.
  *   This tag is processed by
  *   \Drupal\serialization\RegisterSerializationClassesCompilerPass.
+ *
+ * @see http://symfony.com/doc/current/components/serializer.html
+ * @see \Symfony\Component\Serializer\Serializer
  */
 class RegisterSerializationClassesCompilerPass implements CompilerPassInterface {