Example of how to change the description sent to the payment providers to '{Event name} tickets for {attendee_names}'

example.php

<?php //Please do not include the opening PHP tag if you already have one

add_filter( 'FHEE__EE_Gateway___order_description', 
	'my_custom_order_description_with_date', 10, 3 
);
function my_custom_order_description_with_date( $desc, $gateway, $payment ) {
	$desc = '';

	$transaction = $payment->transaction();
	$primary_registrant = $transaction->primary_registration();

	if( $primary_registrant instanceof EE_Registration ) {
		$event = $primary_registrant->event_obj();
		if ( $event instanceof EEI_Event ) {
			$desc = $event->name() . ' '; 
		}
	}

	$desc .= 'tickets for ';

	$primary_registration = $transaction->primary_registration();
	if( $transaction instanceof EEI_Transaction ) {
		$registrations = $transaction->registrations();
		foreach( $registrations as $registration ) {
			if( $registration instanceof EE_Registration ) {
				$attendee = $registration->attendee();
				$desc .= $attendee->full_name() . ', ';
			}
		}
		//Remove triling ', '
		$desc = substr($desc, 0, -2);

	}
	return $desc;
}