Index: src/wp-includes/rest-api.php
===================================================================
--- src/wp-includes/rest-api.php	(revision 43966)
+++ src/wp-includes/rest-api.php	(working copy)
@@ -1112,7 +1112,14 @@
  *
  * @param mixed $value The value to sanitize.
  * @param array $args  Schema array to use for sanitization.
- * @return true|WP_Error
+ * @return int|float|string|array|boolean|mixed Based on the `$args`'s type property, returns `$value`'s type. 
+ * If `$args['type']` is an integer the return value is an int
+ * If `$args['type']` is an number the return value is an float
+ * If `$args['type']` is an string the return value is an float
+ * If `$args['type']` is an array the return value is an array
+ * If `$args['type']` is an array the return value is an array
+ * If `$args['type']` is not neither of these above, then `$args['format']` is looked upon and the return value is a string
+ * If `$args['type']` is not neither of these above and then `$args['format']` is not defined, then the original `$value`is returned
  */
 function rest_sanitize_value_from_schema( $value, $args ) {
 	if ( 'array' === $args['type'] ) {