diff -u b/core/includes/menu.inc b/core/includes/menu.inc
--- b/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -2553,6 +2553,13 @@
   // Fill in the machine name from the array key.
   foreach ($all_links as $machine_name => &$link) {
     $link['machine_name'] = $machine_name;
+
+    // Check for required array keys.
+  if (!isset($link['link_title'])) {
+    throw new \Exception(sprintf('Menu link %s does not have a "link_title" key in its definition.', $machine_name));
+  }
+
+  // Check if the specified parent menu link exists.
     if (isset($link['parent']) && !isset($all_links[$link['parent']])) {
       throw new \OutOfBoundsException(sprintf('Menu link %s specifies it has parent %s, but no menu link with that machine name exists.', $machine_name, $link['parent']));
     }
only in patch2:
unchanged:
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -497,7 +497,7 @@ function hook_menu_get_item_alter(&$router_item, $path, $original_map) {
  *   name, which must be unique. The corresponding array value is an
  *   associative array that may contain the following key-value pairs:
  *   - link_title: (required) The untranslated title of the menu item.
- *   - description: The untranslated description of the link.
+ *   - description: (optional) The untranslated description of the link.
  *   - route_name: (optional) The route name to be used to build the path.
  *     Either a route_name or a link_path must be provided.
  *   - route_parameters: (optional) The route parameters to build the path.