diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
index 4eb1ca7..4f8ca4f 100644
--- a/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/Tables.php
@@ -50,7 +50,20 @@ public function __construct(SelectInterface $sql_query) {
   }
 
   /**
-   * {@inheritdoc}
+   * Adds a field to a database query.
+   *
+   * @param string $field
+   *   If it contains a dot, then field name dot field column. If it doesn't
+   *   then entity property name.
+   * @param string $type
+   *   Join type, can either be INNER or LEFT.
+   * @param $langcode
+   *   The language code the field values are to be shown in.
+   * @throws \Drupal\Core\Entity\Query\QueryException
+   * @return string
+   *   The return value is a string containing the alias of the table, a dot
+   *   and the appropriate SQL column as passed in. This allows the direct use
+   *   of this in a query for a condition or sort.
    */
   public function addField($field, $type, $langcode) {
     $entity_type = $this->sqlQuery->getMetaData('entity_type');
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/TablesInterface.php b/core/lib/Drupal/Core/Entity/Query/Sql/TablesInterface.php
index adf07e6..3e7c399 100644
--- a/core/lib/Drupal/Core/Entity/Query/Sql/TablesInterface.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/TablesInterface.php
@@ -13,12 +13,16 @@
 interface TablesInterface {
 
   /**
+   * Adds a field to a database query.
+   *
    * @param string $field
    *   If it contains a dot, then field name dot field column. If it doesn't
    *   then entity property name.
    * @param string $type
    *   Join type, can either be INNER or LEFT.
-   *
+   * @param $langcode
+   *   The language code the field values are to be shown in.
+   * @throws \Drupal\Core\Entity\Query\QueryException
    * @return string
    *   The return value is a string containing the alias of the table, a dot
    *   and the appropriate SQL column as passed in. This allows the direct use