Many details on the Irish border question are still to be hammered out, a senior unionist warned.
The text agreed between the EU and UK provides “high level” reassurances to launch negotiations around the small print, Ulster Unionist leader Robin Swann added.
He suggested up to 142 areas of cross-border co-operation still needed to be dealt with.
“This is a guide as to the next stage, the next stage will tell you the detail and at that point Northern Ireland will see whether the devil is in the detail or the saviour is in the small print.”
The EU and UK agreed work would continue in a distinct strand of the negotiations on detailed arrangements necessary on Ireland and Northern Ireland.
The joint report said: “Such work will also address issues arising from Ireland’s unique geographic situation, including the transit of goods (to and from Ireland via the United Kingdom).”
Three scenarios were proposed in the text published on Friday.
It initially envisages dealing with issues like protecting trade across Northern Ireland’s invisible land border with the Republic as part of the overall relationship between member states and Britain.
This refrain has been a common one from British Cabinet ministers for months.
If that fails, the text said the UK would propose specific solutions addressing the “unique” circumstances of the island of Ireland.
Only if that is also rejected will the United Kingdom “maintain full alignment with those rules of the Internal Market and the Customs Union which, now or in the future, support North-South co-operation, the all-island economy and the protection of the 1998 Agreement”.
The 1998 Good Friday Agreement largely ended decades of violence and enshrined many of the North-South co-operation measures in an international treaty between Ireland and the UK.
Following the Agreement, politicians and civil servants in Northern Ireland and the Republic worked together on a wide range of areas including tourism, health, waterways and cross-border trade.
Many private sector workers cross the border every day for work and small businesses on both sides of the frontier rely on on its open nature to send goods and labour back and forth.
According to the Intertrade Ireland business organisation, in 2015 total trade in manufacturing came to 3.4 billion euro or £2.47 billion.
Some have suggested many of the trade ties are centred on agriculture.
Mr Swann said political leaders were never going to get detailed agreements on up to 142 areas of cross-border cooperation at this stage.
“This was to get the high-level reassurances to get us to the detailed negotiations.”
The UK said it “remains committed” to protecting North-South co-operation and its guarantee of avoiding a hard border.
The joint report from EU and UK negotiators confirmed: “Any future arrangements must be compatible with these overarching requirements.”
Mr Swann said the responsibilities given to the Northern Ireland Assembly and ministerial Executive made it even more imperative that powersharing was restored after months in the deep freeze.
The text also contained concessions for the DUP, which wants to avoid any disparity between Northern Ireland and the rest of the UK, often referred to as a border in the Irish Sea.
It said: “In the absence of agreed solutions ... the United Kingdom will ensure that no new regulatory barriers develop between Northern Ireland and the rest of the United Kingdom, unless, consistent with the 1998 Agreement, the Northern Ireland Executive and Assembly agree that distinct arrangements are appropriate for Northern Ireland.
“In all circumstances, the United Kingdom will continue to ensure the same unfettered access for Northern Ireland’s businesses to the whole of the United Kingdom internal market.”
The text said the UK and EU will honour existing commitments to programmes like Peace, which supports development of a more peaceful society in Northern Ireland.
It added: “Possibilities for future support will be examined favourably.”