SetCronJob sends its user agent along with with the HTTP request headers to your cronjob URL. The default value is SetCronJob/1.0 (+http://www.setcronjob.com/).
For Gold accounts, you can click Edit cronjob, at the section Send HTTP request, update HTTP headers with this:
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36
For Platinum account and above, you can change the user agent for a specific cronjob by clicking Edit > Send HTTP request, enter desired User agent value, and Save.