diff --git a/includes/_internal.h b/includes/_internal.h
index 943ec00..4195581 100644
--- a/includes/_internal.h
+++ b/includes/_internal.h
@@ -79,6 +79,13 @@ int		flag_p(va_list args, int fd);
  */
 int		flag_percent(va_list args, int fd);
 
+/**
+ * @brief Function to handle the flag s in printf's function
+ *
+ * @param args list of arguments
+ * @param fd file descriptor
+ * @return The number of character write in the fd (always 1)
+ */
 int		flag_s(va_list args, int fd);
 
 int		flag_u(va_list args, int fd);