protected static function get_context_parameters() {
        $id = new external_value(
            PARAM_INT,
            'Context ID. Either use this value, or level and instanceid.',
            VALUE_DEFAULT,
            0
        );
        $level = new external_value(
            PARAM_ALPHA,
            'Context level. To be used with instanceid.',
            VALUE_DEFAULT,
            ''
        );
        $instanceid = new external_value(
            PARAM_INT,
            'Context instance ID. To be used with level',
            VALUE_DEFAULT,
            0
        );
        return new external_single_structure(array(
            'contextid' => $id,
            'contextlevel' => $level,
            'instanceid' => $instanceid,
        ));
    }