May sealed the deal after a pre-dawn dash to Brussels, thereby clearing the way for the start of arduous talks on future trade ties between Britain and the EU after Brexit.
Asked if he thought the deal with the EU was a breakthrough, Corbyn told reporters: "Until I see more of it, no."
Speaking in Geneva after a visit to the United Nations, Corbyn said his party stood ready for another parliamentary election in Britain at any time, noting May's reliance for her majority on Northern Ireland's Democratic Unionist Party (DUP).
"They (the DUP) seem to be calling the shots all the time. They scuppered a deal she was trying to make a few days ago and they clearly put conditions on this, which is why I want to see a much fuller statement than we've had thus far," he said.
The next election in Britain is not due until 2022, but there has been much media speculation that it could come much earlier due to May's lack of a parliamentary majority and deep divisions within her governing Conservative Party over Brexit.
Corbyn said Labour had consistently called for maintaining the benefits of belonging to the EU's customs union and single market during a transitional period as Britain leaves the bloc.
"The transitional period is unspecific and I think she needs to bring some clarity to that," he said.
The transition should be long enough to guarantee UK and EU jobs and to deal with common problems, such as regulating airspace, he said. It should also ensure that consumers', workers' and environmental rights were put into British law.
"The statements that have been made this morning do not specify what regulatory framework there will be in the future and that remains to be seen, because there are still many people in the Conservative Party who want to live in a de-regulated environment, where Britain basically lowers wages and conditions and the tax take on large corporations."
Corbyn said he hoped Friday's deal included sections on the rights of family reunion for EU and British citizens, adding they should be granted unilaterally and not negotiated.
A reference in the deal to involving the European Court of Justice on citizenship issues for up to eight years was a sign that the government accepted the need for judicial oversight of citizens' rights, he said.