diff --git a/src/Cnp.php b/src/Cnp.php
index 1e1998d..b213c1c 100644
--- a/src/Cnp.php
+++ b/src/Cnp.php
@@ -4,12 +4,22 @@
 class Cnp
 {
 
+    /**
+     * @param $cnp
+     *
+     * @return bool
+     */
     public static function invalid($cnp)
     {
         return ! static::valid($cnp);
     }
 
 
+    /**
+     * @param $p_cnp
+     *
+     * @return bool
+     */
     public static function valid($p_cnp)
     {
         // CNP must have 13 characters