nice, you can find documentation customization of woo commerce tab at https://docs.woothemes.com/document/editing-product-data-tabs/
but if you have an empty tab’s content, your tab will generated tab without label and content. you can tweak it by yourself.
i.e:
if ( ! empty ( $tabs['description'] ) ) {
$tabs['description']['priority'] = 25; // Description second
}
thank you.