If you have hand-written code to make GET requests to /sentry with requestType of 1 (token) or 2 (auth), you will need to change this to make a POST request instead as we will be disallowing GET requests in future. The "token" parameter must be moved out of the URL query and into the POST body. Other requestTypes such as 4 and 5 (user lookup) are fine to request as a GET.
We'll try to contact most of the people who we know are making such requests, but we can't reliably detect every application so you may wish to review your code now to avoid any loss of service for users.