There’s a reason why you start explaining games to a new player by all playing with cards facing up the first round. By having complete information you can get an overview and can arrive at good decisions more quickly, without having to guess and worry about taking risks. In competitive games you would like to close your cards again once the new player has a grasp of the rules, as the whole point of the game is finding out who is best in making decisions and taking risks while not knowing what resources the others hold. In cooperative situations you should stay in this mindset of radical transparency and keep playing with open cards.
In a cooperation you’re not fighting each other, but building something together, fighting against something together or profiting from something together. Whether it is building a great company with colleagues, having the most loving relationship with your partner or nourishing a vegetable garden with devotees, you all win or lose simultaneously. Do not hold back on sharing your ideas, worries, boundaries, resources, etc. You have a much better collaboration with quicker and better results by all being transparent.
An apparent downside to transparency is that unsolvable problems will break up collaborations quicker than by not being transparent. You might question whether this downside is an actual downside, as the problem will persist anyways and will probably surface sometime in the future. This makes you stuck in a similar position, only further down the line with more commitments and responsibilities added to the situation. Transparency can only resolve problems that are in essence resolvable. It is not a magical cure, except transparency might lead to understanding which in some cases can be enough to tolerate unresolved problems, which is also a fair resolution.