diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index b5eff61a06..2e04a39087 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -5854,7 +5854,15 @@ function wp_delete_attachment_files( $post_id, $meta, $backup_sizes, $file ) {
  *
  * @param int  $attachment_id Attachment post ID. Defaults to global $post.
  * @param bool $unfiltered    Optional. If true, filters are not run. Default false.
- * @return mixed Attachment meta field. False on failure.
+ * @return (array|boolean) {
+ *     Attachment meta field. False on failure.
+ * 
+ *     @type integer $width    The height of the attachment
+ *     @type integer $height   The width of the attachment.
+ *     @type string $file      The file path relative to `wp-content/uploads/`
+ *     @type array $sizes      Keys are size slugs, each value is an array containing 'file', 'width', 'height', and 'mime-type'
+ *     @type array $image_meta
+ * }
  */
 function wp_get_attachment_metadata( $attachment_id = 0, $unfiltered = false ) {
 	$attachment_id = (int) $attachment_id;