I don't know why you were downvoted, they literally state in their terms of service they will do this:
""" Apps installed with Eager may, for example:
Add cookies to your domain to track visitors. """
""" Apps installed with Eager may, for example:
Add cookies to your domain to track visitors. """
https://github.com/EagerApps/Snow https://github.com/EagerApps/SnowPro
If you don't want to do this and will not do this then make it plain in your terms and conditions.
The nice thing about delivering software directly to the client as we do is you can examine the exact code which gets sent, and confirm that it is what you expect.