diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index 568e6c2..364ea18 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -521,8 +521,8 @@ function aggregator_category_load($cid) {
  *
  * @param array $variables
  *   An associative array containing:
- *   - item: The item to be displayed.
- *   - feed: Not used.
+ *   - url: URL to the feed item.
+ *   - title: Title of the feed item.
  */
 function template_preprocess_aggregator_block_item(&$variables) {
   // Display the external link to the item.
diff --git a/core/modules/aggregator/templates/aggregator-page-opml.html.twig b/core/modules/aggregator/templates/aggregator-page-opml.html.twig
index 035d76c..8640aab 100644
--- a/core/modules/aggregator/templates/aggregator-page-opml.html.twig
+++ b/core/modules/aggregator/templates/aggregator-page-opml.html.twig
@@ -4,11 +4,11 @@
  * Default theme implementation to present @todo.
  *
  * Available variables:
- * - title: @todo.
- * - date: @todo.
- * - feeds: @todo.
- *   - feed.title: @todo.
- *   - feed.url: @todo.
+ * - title: Title of the feed.
+ * - date: Last date feed was modified.
+ * - feeds: An associative array of feed items containing:
+ *   - feed.title: Title of the feed item.
+ *   - feed.url: URL to the feed item.
  *
  * @see template_preprocess()
  * @see template_preprocess_aggregator_page_opml()
diff --git a/core/modules/aggregator/templates/aggregator-page-rss.html.twig b/core/modules/aggregator/templates/aggregator-page-rss.html.twig
index 9ad37ea..1075842 100644
--- a/core/modules/aggregator/templates/aggregator-page-rss.html.twig
+++ b/core/modules/aggregator/templates/aggregator-page-rss.html.twig
@@ -9,6 +9,7 @@
  * - description: RSS channel description.
  * - language: RSS channel language code.
  * - items: RSS feed items.
+ * - args: Any channel args to be rendered after the language code.
  *
  * @see template_preprocess()
  * @see template_preprocess_aggregator_page_rss()