As a customer, you are not obligated to hand out a tip to the on-site employees. However, it is a nice gesture to express your appreciation for the service. If you choose to give a tip, there are a few things to consider.
It's also important to note that the tip should be given directly to the employee. If you add the tip to the bill, the employee may not receive it. It's best to give the tip in cash and hand it directly to the employee.
If you are unsure whether you should give a tip or how much is appropriate, you can simply ask. Politely inquire with the employee if they accept tips and what would be considered reasonable. Most employees will be happy to assist you.