diff --git a/core/lib/Drupal/Core/Database/database.api.php b/core/lib/Drupal/Core/Database/database.api.php
index 3e0fbf8..59c65d6 100644
--- a/core/lib/Drupal/Core/Database/database.api.php
+++ b/core/lib/Drupal/Core/Database/database.api.php
@@ -313,6 +313,12 @@
  *    specification). Each specification is an array of one or more
  *    key column specifiers (see below) that form an index on the
  *    table.
+ *  - mysql_engine: The storage engine to use in MySQL databases like InnoDB
+ *    or MyISAM, default to InnoDB engine.
+ *  - mysql_character_set: In MySQL databases, the character encoding type
+ *    for stored data, example UTF8.
+ *  - collation: In MySQL databases, a set of rules that defines how to compare
+ *    and sort character strings, example utf8_bin format.
  *
  * A key column specifier is either a string naming a column or an
  * array of two elements, column name and length, specifying a prefix