An agent is a person who acts on behalf of another person, so all agents are, in effect, employees

To be directed in one's actions by another as part of a freely agreed upon contract in which services are exchanged for pay is exactly what it is to be an employee. This definition, in fact, is written into American labor law. So what does an agent do? An agent acts on behalf of a client and at the client's direction in exchange for monetary compensation. This exactly fits the definition of an employee, therefore an agent is an employee.