diff --git a/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkit.php b/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkit.php
index 4615847..a73e5e2 100644
--- a/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkit.php
+++ b/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkit.php
@@ -12,10 +12,21 @@
 /**
  * Defines a Plugin annotation object for the image toolkit plugin.
  *
- * @Annotation
+ * An image toolkit provides common image file manipulations like scaling,
+ * cropping, and rotating.
+ *
+ * Plugin namespace: Plugin\ImageToolkit
+ *
+ * For a working example, see
+ * \Drupal\system\Plugin\ImageToolkit\GDToolkit
  *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation
  * @see \Drupal\Core\ImageToolkit\ImageToolkitInterface
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitBase
  * @see \Drupal\Core\ImageToolkit\ImageToolkitManager
+ * @see plugin_api
+ *
+ * @Annotation
  */
 class ImageToolkit extends Plugin {
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkitOperation.php b/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkitOperation.php
index 59e9fb0..0e0dbb2 100644
--- a/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkitOperation.php
+++ b/core/lib/Drupal/Core/ImageToolkit/Annotation/ImageToolkitOperation.php
@@ -12,9 +12,23 @@
 /**
  * Defines a Plugin annotation object for the image toolkit operation plugin.
  *
- * @Annotation
+ * An image toolkit operation plugin provides a self-contained image
+ * manipulation routine, for a specific image toolkit. Examples of image
+ * toolkit operations are scaling, cropping, rotating, etc.
+ *
+ * Plugin namespace: Plugin\ImageToolkit\Operation
+ *
+ * For a working example, see
+ * \Drupal\system\Plugin\ImageToolkit\Operation\gd\Crop
  *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkit
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationInterface
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationBase
  * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationManager
+ * @see plugin_api
+ *
+ * @Annotation
  */
 class ImageToolkitOperation extends Plugin {
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitBase.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitBase.php
index 1a5c19b..793768c 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitBase.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitBase.php
@@ -12,6 +12,14 @@
 use Drupal\Core\Plugin\PluginBase;
 use Psr\Log\LoggerInterface;
 
+/**
+ * Provides a base class for image toolkit plugins.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkit
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitInterface
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitManager
+ * @see plugin_api
+ */
 abstract class ImageToolkitBase extends PluginBase implements ImageToolkitInterface {
 
   /**
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
index b50331a..b198af8 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
@@ -43,6 +43,11 @@
  *
  * An image toolkit provides common image file manipulations like scaling,
  * cropping, and rotating.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkit
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitBase
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitManager
+ * @see plugin_api
  */
 interface ImageToolkitInterface extends PluginInspectionInterface {
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitManager.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitManager.php
index 270f870..69e2f1c 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitManager.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitManager.php
@@ -15,7 +15,12 @@
 use Psr\Log\LoggerInterface;
 
 /**
- * Manages toolkit plugins.
+ * Manages image toolkit plugins.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkit
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitInterface
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitBase
+ * @see plugin_api
  */
 class ImageToolkitManager extends DefaultPluginManager {
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationBase.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationBase.php
index eb13a9f..9bff2a4 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationBase.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationBase.php
@@ -12,6 +12,14 @@
 use Drupal\Core\Plugin\PluginBase;
 use Psr\Log\LoggerInterface;
 
+/**
+ * Provides a base class for image toolkit operation plugins.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationInterface
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationManager
+ * @see plugin_api
+ */
 abstract class ImageToolkitOperationBase extends PluginBase implements ImageToolkitOperationInterface {
 
   /**
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationInterface.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationInterface.php
index 8cd9da3..779deef 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationInterface.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationInterface.php
@@ -15,6 +15,11 @@
  * An image toolkit operation plugin provides a self-contained image
  * manipulation routine, for a specific image toolkit. Examples of image
  * toolkit operations are scaling, cropping, rotating, etc.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationBase
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationManager
+ * @see plugin_api
  */
 interface ImageToolkitOperationInterface extends PluginInspectionInterface {
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationManager.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationManager.php
index 20ecc55..ae7d0dd 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationManager.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationManager.php
@@ -17,6 +17,11 @@
 
 /**
  * Manages toolkit operation plugins.
+ *
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationBase
+ * @see \Drupal\Core\ImageToolkit\ImageToolkitOperationInterface
+ * @see plugin_api
  */
 class ImageToolkitOperationManager extends DefaultPluginManager implements ImageToolkitOperationManagerInterface {
 
diff --git a/core/modules/image/src/Annotation/ImageEffect.php b/core/modules/image/src/Annotation/ImageEffect.php
index 3a6f763..1f742b3 100644
--- a/core/modules/image/src/Annotation/ImageEffect.php
+++ b/core/modules/image/src/Annotation/ImageEffect.php
@@ -12,7 +12,19 @@
 /**
  * Defines an image effect annotation object.
  *
+ * Plugin Namespace: Plugin\ImageEffect
+ *
+ * For a working example, see
+ * \Drupal\image\Plugin\ImageEffect\ResizeImageEffect
+ *
  * @see hook_image_effect_info_alter()
+ * @see \Drupal\image\ConfigurableImageEffectInterface
+ * @see \Drupal\image\ConfigurableImageEffectBase
+ * @see \Drupal\image\ImageEffectInterface
+ * @see \Drupal\image\ImageEffectBase
+ * @see \Drupal\image\ImageEffectManager
+ * @see \Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation
+ * @see plugin_api
  *
  * @Annotation
  */
diff --git a/core/modules/image/src/ConfigurableImageEffectBase.php b/core/modules/image/src/ConfigurableImageEffectBase.php
index 7b391b5..5a399ac 100644
--- a/core/modules/image/src/ConfigurableImageEffectBase.php
+++ b/core/modules/image/src/ConfigurableImageEffectBase.php
@@ -11,6 +11,13 @@
 
 /**
  * Provides a base class for configurable image effects.
+ *
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\image\ConfigurableImageEffectInterface
+ * @see \Drupal\image\ImageEffectInterface
+ * @see \Drupal\image\ImageEffectBase
+ * @see \Drupal\image\ImageEffectManager
+ * @see plugin_api
  */
 abstract class ConfigurableImageEffectBase extends ImageEffectBase implements ConfigurableImageEffectInterface {
 
diff --git a/core/modules/image/src/ConfigurableImageEffectInterface.php b/core/modules/image/src/ConfigurableImageEffectInterface.php
index 0f57994..bc47f9e 100644
--- a/core/modules/image/src/ConfigurableImageEffectInterface.php
+++ b/core/modules/image/src/ConfigurableImageEffectInterface.php
@@ -11,6 +11,13 @@
 
 /**
  * Defines the interface for configurable image effects.
+ *
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\image\ConfigurableImageEffectBase
+ * @see \Drupal\image\ImageEffectInterface
+ * @see \Drupal\image\ImageEffectBase
+ * @see \Drupal\image\ImageEffectManager
+ * @see plugin_api
  */
 interface ConfigurableImageEffectInterface extends ImageEffectInterface, PluginFormInterface {
 }
diff --git a/core/modules/image/src/ImageEffectBase.php b/core/modules/image/src/ImageEffectBase.php
index dac7966..6714dd8 100644
--- a/core/modules/image/src/ImageEffectBase.php
+++ b/core/modules/image/src/ImageEffectBase.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\image\Annotation\ImageEffectBase.
+ * Contains \Drupal\image\ImageEffectBase.
  */
 
 namespace Drupal\image;
@@ -14,6 +14,13 @@
 
 /**
  * Provides a base class for image effects.
+ *
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\image\ImageEffectInterface
+ * @see \Drupal\image\ConfigurableImageEffectInterface
+ * @see \Drupal\image\ConfigurableImageEffectBase
+ * @see \Drupal\image\ImageEffectManager
+ * @see plugin_api
  */
 abstract class ImageEffectBase extends PluginBase implements ImageEffectInterface, ContainerFactoryPluginInterface {
 
diff --git a/core/modules/image/src/ImageEffectInterface.php b/core/modules/image/src/ImageEffectInterface.php
index d2db1cd..b0ea2ea 100644
--- a/core/modules/image/src/ImageEffectInterface.php
+++ b/core/modules/image/src/ImageEffectInterface.php
@@ -13,6 +13,13 @@
 
 /**
  * Defines the interface for image effects.
+ *
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\image\ImageEffectBase
+ * @see \Drupal\image\ConfigurableImageEffectInterface
+ * @see \Drupal\image\ConfigurableImageEffectBase
+ * @see \Drupal\image\ImageEffectManager
+ * @see plugin_api
  */
 interface ImageEffectInterface extends PluginInspectionInterface, ConfigurablePluginInterface {
 
diff --git a/core/modules/image/src/ImageEffectManager.php b/core/modules/image/src/ImageEffectManager.php
index 4885450..762f947 100644
--- a/core/modules/image/src/ImageEffectManager.php
+++ b/core/modules/image/src/ImageEffectManager.php
@@ -13,6 +13,14 @@
 
 /**
  * Manages image effect plugins.
+ *
+ * @see hook_image_effect_info_alter()
+ * @see \Drupal\image\Annotation\ImageEffect
+ * @see \Drupal\image\ConfigurableImageEffectInterface
+ * @see \Drupal\image\ConfigurableImageEffectBase
+ * @see \Drupal\image\ImageEffectInterface
+ * @see \Drupal\image\ImageEffectBase
+ * @see plugin_api
  */
 class ImageEffectManager extends DefaultPluginManager {