TFS Service hook should not fire when work item is updated via REST API
The service hook will fire as part of the notifications process.  You can suppress all notifications by setting the URI parameter suppressNotifications to true.

An example request URI might be:

PATCH https://dev.azure.com/fabrikam/_apis/wit/workitems/{id}?suppressNotifications=true&amp;api-version=5.0


See the work item update API documentation for more information.