public static function createDefault()
    {
        $agent = new static();

        $options = ['Guzzle/' . ClientInterface::VERSION];
        if (extension_loaded('curl')) {
            $options[] = 'curl/' . curl_version()['version'];
        }

        return $agent
            ->setField('Library', static::NAME, static::VERSION, $options)
            ->setField('OS', php_uname('s'), php_uname('r'))
            ->setField('Language', 'PHP', phpversion());
    }