Agents are able to see when appointments are booked on your listing. However, your listing agent can set appointments on your listing to be exclusive or overlapping.
An exclusive showing will only allow one buyer's agent and buyer in your home at a specified time.
Overlapping showings (also known as double-booking), where more than one agent can see your home at the same time, can be beneficial.
If you want to prevent overlapping showings, you can contact your listing agent