Do I have to accept an oral settlement offer that I agreed to dollar amount but I was unaware of additional terms?

That depends.  If you, or your lawyer, agreed subject to execution of a formal written agreement (which is often the case with settlement agreements), then you have no contract.  For example, if you said "I agree, write it up.", you may have a contract; if you said "I agree, we'll work out the details in the paperwork" you probably don't have a contract.  Also, in some jurisdictions (I don't know about Minnesota), a settlement agreement may have to be in writing, or agreed to in open court, to be binding, and there may be additional formalities required. Assuming that there is no need for a signed writing for a valid settlement agreement in Minnesota, the question is whether you are bound by the additional terms.  Unfortunately, I don't think the answer is black and white.  Normally, there is no contract unless both sides have agreed on all material terms (I'm assuming that the terms to which you object are material).  Here, although you may not have agreed to all material terms, you may be bound by your lawyer's agreement, as he is your agent.  Did your lawyer know that you had not seen his email with the additional terms?  If he thought that you had seen that email and had agreed to the other terms, and he communicated acceptance to the other side, you may be bound by it.  EVen if he knew you had not seen the additional terms, but accepted on your behalf anyway, you could be bound by it (although you could sue the lawyer.)  Alternatively, the agreement might be considered void for mutual mistake; you thought you were agreeing to one thing while the other side thought you were agreeing to something else. I'm sorry I can't give you a short final answer.  If a settlement agreement has to be written and signed to be valid, you're ok.  If not, there are questions.