Automated site monitoring scripts

Automated site monitoring scripts expect the site to be same always - that means either ALWAYS get survey invite, or NEVER get invite. What settings decide when to invite (invite the automated monitoring tool to take survey), and when not? Is it a combination of Inviation rate defined in the account, cookie in browser, and a java-script timer?

What are best practices you follow while dealing with site monitoring tools?

Thanks,
Byju Joy