diff --git a/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php b/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
index e355850..27b8273 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
@@ -13,7 +13,14 @@
 use Drupal\migrate\Row;
 
 /**
- * The base class for all source plugins.
+ * The base class for source plugins.
+ *
+ * Available configuration keys:
+ * - cache_counts: (optional) (Integer) If set cache the source count.
+ * - skip_count: (optional) (Integer) If set not attempt to count the source.
+ * - track_changes: (optional) (Integer) If set track changes to incoming data.
+ * - high_water_property: It is an array of single value (optional table alias)
+ *   which have the high_water_property corresponding to it.
  *
  * @see \Drupal\migrate\Plugin\MigratePluginManager
  * @see \Drupal\migrate\Annotation\MigrateSource