Federal prosecutors say as early as 1981 and continuing to present day, former U.S. Ambassador to Bolivia Manuel Rocha secretly supported Cuba and its intelligence services by serving as an agent for the communist government against the U.S.
As part of his alleged role, Rocha attained high-level diplomatic positions that provided him access to classified information and abilities to affect U.S. foreign policy.
“ROCHA always kept his status as a Cuban agent secret in order to protect himself and others and to allow himself the opportunity to engage in additional clandestine activity,” prosecutors said Monday in a newly unsealed criminal complaint.
I don’t believe that’s not what “agent” means in this context. It means that he was representing Cuba’s interests in negotiations. He wouldn’t necessarily be spying for them.
https://en.wikipedia.org/wiki/Foreign_Agents_Registration_Act