Thanks for your concern, but I believe that to be a “federal agent” one must be employed by the feds, or be a contractor for the feds. Someone who simply reports information to them - like an accountant or a doctor - is not a federal agent. If so, then every employer in the country would be a federal agent by dint of reporting their employees’ wages to the IRS.
Anyhow, I will not disclose the ownership of any item of my property to any person who does not have a need to know - with ME being the person who determines the “need to know.”
Such as a doctor receiving federal payments, especially as Obamacare ramps up and takes over?
It doesn't matter what we believe; it's whatever a federal court decides. It's not a stretch to think a court could decide any health care provider who receives payment from the federal government and is being directed by the federal government to ask questions pertaining to your health is a contractor and thus a federal agent.
Regardless, I wouldn't lie. I'd remind them why I came to their office and suggest we focus on that. If they persist, I'd simply refuse to answer.