OK, I figured out how to print the description in the mail: <?php echo ($details); ?>

Another question: I would like to have a certain message if the balance is zero; a different message if the balance is not. I have not been able to successfully identify how to compare the balance to zero. I tried this:

if (woo_wallet()->wallet->get_wallet_balance( $user->ID ) == 0)

but it always resolves to true, whether or not the balance is zero, even though this line

<p><?php _e(‘Your current balance is:’) ?> <?php echo woo_wallet()->wallet->get_wallet_balance( $user->ID ); ?></p>

displays a correct non-zero balance in the email.