diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index 9f4e1ac74a..d29ae479ec 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -65,10 +65,15 @@ function get_category_parents( $id, $link = false, $separator = '/', $nicename =
 /**
  * Retrieve post categories.
  *
+ * This tag may be used outside The Loop by passing a post id as the parameter.
+ *
+ * Note: This function only returns results from the default "category" taxonomy.
+ * For custom taxonomies use get_the_terms().
+ *
  * @since 0.71
  *
  * @param int $id Optional, default to current post ID. The post ID.
- * @return array
+ * @return array Array of objects, one for each category assigned to the post.
  */
 function get_the_category( $id = false ) {
 	$categories = get_the_terms( $id, 'category' );