WordPress at a glance
action is not described

wp_feed_options action-hook . WP 3.0.0

Fires just before processing the SimplePie feed object.

Usage

add_action( 'wp_feed_options', 'action_function_name_5529', 10, 2 );
function action_function_name_5529( $feed, $url ){
	// action...
}
$feed(object)
SimplePie feed object (passed by reference).
$url(mixed)
URL of feed to retrieve. If an array of URLs, the feeds are merged.

Where the hook is called

fetch_feed()
wp-includes/feed.php 702
do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );

Where the hook is used (in WP core)

Does not used.