WordPress at a glance
action is not described

add_meta_boxes_(post_type) action-hook . WP 3.0.0

Fires after all built-in meta boxes have been added, contextually for the given post type.

The dynamic portion of the hook, $post_type, refers to the post type of the post.

Usage

add_action( 'add_meta_boxes_(post_type)', 'action_function_name_5661' );
function action_function_name_5661( $post ){
	// action...
}
$post(WP_Post)
Post object.

Where the hook is called

register_and_do_post_meta_boxes()
wp-admin/includes/meta-boxes.php 1427
do_action( "add_meta_boxes_{$post_type}", $post );

Where the hook is used (in WP core)

Does not used.