Ministers will be forced to publish the government's full legal advice on the deal after MPs found them in contempt of Parliament for issuing a summary.
And MPs backed a motion giving the Commons a direct say in what happens if her deal is rejected next Tuesday.
Mrs May said MPs had a duty to deliver on the 2016 Brexit vote and the deal on offer was an "honourable compromise".
Addressing the Commons at the start of a five-day debate on her proposed Brexit agreement, Mrs May said Brexit divisions had become "corrosive" to UK politics and the public believed the issue had "gone on long enough" and must be resolved.
MPs will decide whether to reject the terms of the UK's withdrawal and future relations with the EU on Tuesday 11 December.