public static function get_discussion_posts_parameters() {
        return new external_function_parameters ([
            'discussionid' => new external_value(PARAM_INT, 'The ID of the discussion from which to fetch posts.', VALUE_REQUIRED),
            'sortby' => new external_value(PARAM_ALPHA, 'Sort by this element: id, created or modified', VALUE_DEFAULT, 'created'),
            'sortdirection' => new external_value(PARAM_ALPHA, 'Sort direction: ASC or DESC', VALUE_DEFAULT, 'DESC')
        ]);
    }