diff --git a/core/modules/aggregator/src/Annotation/AggregatorFetcher.php b/core/modules/aggregator/src/Annotation/AggregatorFetcher.php
index 0fbee2fe37d5..db66347196f5 100644
--- a/core/modules/aggregator/src/Annotation/AggregatorFetcher.php
+++ b/core/modules/aggregator/src/Annotation/AggregatorFetcher.php
@@ -12,6 +12,15 @@ use Drupal\Component\Annotation\Plugin;
 /**
  * Defines a Plugin annotation object for aggregator fetcher plugins.
  *
+ * Plugin Namespace: Plugin\aggregator\fetcher
+ *
+ * For a working example, see \Drupal\aggregator\Plugin\aggregator\fetcher\DefaultFetcher
+ *
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see \Drupal\aggregator\Plugin\FetcherInterface
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see plugin_api
+ *
  * @Annotation
  */
 class AggregatorFetcher extends Plugin {
diff --git a/core/modules/aggregator/src/Annotation/AggregatorParser.php b/core/modules/aggregator/src/Annotation/AggregatorParser.php
index c36a5e883f5a..45842b6e6929 100644
--- a/core/modules/aggregator/src/Annotation/AggregatorParser.php
+++ b/core/modules/aggregator/src/Annotation/AggregatorParser.php
@@ -12,6 +12,15 @@ use Drupal\Component\Annotation\Plugin;
 /**
  * Defines a Plugin annotation object for aggregator parser plugins.
  *
+ * Plugin Namespace: Plugin\aggregator\parser
+ *
+ * For a working example, see \Drupal\aggregator\Plugin\aggregator\parser\DefaultParser
+ *
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see \Drupal\aggregator\Plugin\ParserInterface
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see plugin_api
+ *
  * @Annotation
  */
 class AggregatorParser extends Plugin {
diff --git a/core/modules/aggregator/src/Annotation/AggregatorProcessor.php b/core/modules/aggregator/src/Annotation/AggregatorProcessor.php
index 7ab4827494b6..3aaba5ba3c76 100644
--- a/core/modules/aggregator/src/Annotation/AggregatorProcessor.php
+++ b/core/modules/aggregator/src/Annotation/AggregatorProcessor.php
@@ -12,6 +12,15 @@ use Drupal\Component\Annotation\Plugin;
 /**
  * Defines a Plugin annotation object for aggregator processor plugins.
  *
+ * Plugin Namespace: Plugin\aggregator\processor
+ *
+ * For a working example, see \Drupal\aggregator\Plugin\aggregator\processor\DefaultProcessor
+ *
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see \Drupal\aggregator\Plugin\ProcessorInterface
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see plugin_api
+ *
  * @Annotation
  */
 class AggregatorProcessor extends Plugin {
diff --git a/core/modules/aggregator/src/Plugin/AggregatorPluginManager.php b/core/modules/aggregator/src/Plugin/AggregatorPluginManager.php
index 84196cd17e57..53c3acd8b315 100644
--- a/core/modules/aggregator/src/Plugin/AggregatorPluginManager.php
+++ b/core/modules/aggregator/src/Plugin/AggregatorPluginManager.php
@@ -13,6 +13,15 @@ use Drupal\Core\Plugin\DefaultPluginManager;
 
 /**
  * Manages aggregator plugins.
+ *
+ * @see \Drupal\aggregator\Annotation\AggregatorParser
+ * @see \Drupal\aggregator\Annotation\AggregatorFetcher
+ * @see \Drupal\aggregator\Annotation\AggregatorProcessor
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see \Drupal\aggregator\Plugin\FetcherInterface
+ * @see \Drupal\aggregator\Plugin\ProcessorInterface
+ * @see \Drupal\aggregator\Plugin\ParserInterface
+ * @see plugin_api
  */
 class AggregatorPluginManager extends DefaultPluginManager {
 
diff --git a/core/modules/aggregator/src/Plugin/AggregatorPluginSettingsBase.php b/core/modules/aggregator/src/Plugin/AggregatorPluginSettingsBase.php
index 80493c056386..ee94c7c5185e 100644
--- a/core/modules/aggregator/src/Plugin/AggregatorPluginSettingsBase.php
+++ b/core/modules/aggregator/src/Plugin/AggregatorPluginSettingsBase.php
@@ -13,6 +13,15 @@ use Drupal\Core\Plugin\PluginFormInterface;
 
 /**
  * Base class for aggregator plugins that implement settings forms.
+ *
+ * @see \Drupal\aggregator\Annotation\AggregatorParser
+ * @see \Drupal\aggregator\Annotation\AggregatorFetcher
+ * @see \Drupal\aggregator\Annotation\AggregatorProcessor
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see \Drupal\aggregator\Plugin\FetcherInterface
+ * @see \Drupal\aggregator\Plugin\ProcessorInterface
+ * @see \Drupal\aggregator\Plugin\ParserInterface
+ * @see plugin_api
  */
 abstract class AggregatorPluginSettingsBase extends PluginBase implements PluginFormInterface, ConfigurablePluginInterface {
 
diff --git a/core/modules/aggregator/src/Plugin/FetcherInterface.php b/core/modules/aggregator/src/Plugin/FetcherInterface.php
index 65567fa8e131..be9734e75e99 100644
--- a/core/modules/aggregator/src/Plugin/FetcherInterface.php
+++ b/core/modules/aggregator/src/Plugin/FetcherInterface.php
@@ -17,6 +17,11 @@ use Drupal\aggregator\FeedInterface;
  * active fetcher; second, it is converted to a common format by the active
  * parser; and finally, it is passed to all active processors, which manipulate
  * or store the data.
+ *
+ * @see \Drupal\aggregator\Annotation\AggregatorFetcher
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see plugin_api
  */
 interface FetcherInterface {
 
diff --git a/core/modules/aggregator/src/Plugin/ParserInterface.php b/core/modules/aggregator/src/Plugin/ParserInterface.php
index 8a4db68bc19e..bb065a195367 100644
--- a/core/modules/aggregator/src/Plugin/ParserInterface.php
+++ b/core/modules/aggregator/src/Plugin/ParserInterface.php
@@ -18,6 +18,10 @@ use Drupal\aggregator\FeedInterface;
  * active parser; and finally, it is passed to all active processors which
  * manipulate or store the data.
  *
+ * @see \Drupal\aggregator\Annotation\AggregatorParser
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see plugin_api
  */
 interface ParserInterface {
 
diff --git a/core/modules/aggregator/src/Plugin/ProcessorInterface.php b/core/modules/aggregator/src/Plugin/ProcessorInterface.php
index 1b51e2436ab0..6315b4dfd116 100644
--- a/core/modules/aggregator/src/Plugin/ProcessorInterface.php
+++ b/core/modules/aggregator/src/Plugin/ProcessorInterface.php
@@ -17,6 +17,11 @@ use Drupal\aggregator\FeedInterface;
  * active fetcher; second, it is converted to a common format by the active
  * parser; and finally, it is passed to all active processors that manipulate or
  * store the data.
+ *
+ * @see \Drupal\aggregator\Annotation\AggregatorProcessor
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase
+ * @see \Drupal\aggregator\Plugin\AggregatorPluginManager
+ * @see plugin_api
  */
 interface ProcessorInterface {