That's right, just an up-or-down vote. This is the way international agreements get made because it isn't realistic to expect another country to negotiate with 535 members of congress. Someone has to speak for the US, and in our system that's the executive.
Congress can accept or reject what the executive negotiates, but the time for their input is before the negotiation is final. If they want something changed, lobby the negotiators for it now. If they don't get what they want, they can vote against the bill. They just can't micromanage after the parties have agreed.
What knee slapping joke. We are finished in this country!!