Writers are always being told to “Write for the Reader.” It means writing the script in a way that helps the Reader follow it and understand it. The Writer has lived with their story and their characters for weeks, months, maybe even years. The Reader is coming in cold. In one sitting, Readers have to keep track of all the characters which is required to follow the plot and understand the story and oftentimes also write a synopsis of the script.
Most characters are going to be referenced, both in Action/Description and in Dialogue, by their first name: Bill, Mary, Antonio, Jim, Karen, Julio, David, etc. Some scripts have dozens of named characters and by the eighth or ninth character they start to get harder and harder to keep straight. Depending on the type of story and genre, some characters will have titles: Doctor, Detective, Chief, Pastor, Professor, etc. Adding their title is a great way to differentiate them. I’m always surprised by the number of scripts I read in which a character is a doctor, a detective, a chief of some kind, or a pastor, and yet the script doesn’t refer to them as such.
Let's say your story has a detective or two, a chief, a deputy, maybe some officers. You've got a character named Jim Sanderson and he's a detective. Referring to Jim Sanderson as Det. Sanderson in the Action/Description and Character names will make it that much easier for the Reader to distinguish Jim from the other characters. And that will make it that much easier for the Reader to follow the plot. That doesn't mean that characters have to refer to each other in the Dialogue by their titles, only if it's organic to the scene.
Action Item for Writers: Go through your script, find the doctors, professors, and detectives, and add their character titles to the Action/Description and Character names where applicable.