You don’t have to spell out every single thing that you think they might want to know. Have some faith that your callers will be able to figure things out on their own. Be natural but informative.
Use your judgment to choose times that will be best for them based on what you know to be true about their industry and work environment.

Hello, you have reached the reception of Dr. X please leave your name, reason for calling, and your number so I can call you back as soon as I can. If you are experiencing a medical emergency please hang up and dial 911.
I have a confession to make: I haven’t recorded a new voicemail greeting since 2014. In the past four years, I (hopefully) have become more articulate, poised, and self-assured. But hear my voicemail recording, and you’d think I was still new to the work world, a little unsure of myself — and probably not an authority. Obviously I need toupdate it. And if you haven’t changed your voicemail greeting in over a year, you’re likely in the same boat. After all, a professional voicemail recording boosts your credibility, makes you seem more competent, and encourages whoever’s listening to it to continue the relationship. A relatively unprofessional one — like mine, for instance — does the opposite: It encourages prospects, recruiters, and potential connections to run in the other direction. With that in mind, I’ve written 18 unique voicemail greetings for every situation. Pick your favorite, practice a few times, then record your new voicemail.