Write the way the desk already talks
Use your business name, the way you say the hours, and the phrases your staff already trust. 'We're at lunch until one thirty' is better than a generic closed message. Say numbers in words. Do not stack the same fact twice unless the caller asks to hear it again.
Give the agent a short role for the industry. A dealership confirms the department and stays inside the inventory list. A clinic states the office status before it handles a clinical concern. A home-service company offers a message and a callback window instead of promising a technician who is not scheduled.
Cut anything it is not allowed to say
If a sentence is not in the base card or the knowledge notes, it is not part of the voice. That includes other clients' details. One call, one business. The agent that sounds most like you is the one that refuses to guess.