Great quote about the primary goals for any actor’s headshot:
Your goal with your headshot is to:
Provide agents with what they need to help you get work. A good head shot can get you a good agent who can help you get into more auditions and increase your chance of being cast in roles you are seeking.
Provide casting directors with your details so that they can determine whether or not you are suitable for a role. After an audition the director will likely have taken notes and put that with your headshot to help trigger memories of your audition so they can decide whether or not to do a call back.
Keep your headshot updated so your agent and casting directors can match you with roles that fit your current look.