It’s both ways.
Fairness is allowing oneself to be accountable to the other and expecting that the other does the same.
Accountability is a way to care for one another and what one has promised or agreed to. It includes doubts, that is promises one didn’t know the other understood.
What accountability is not, is doing everything the other believes has been promised or assumed to be expectable. Fairness involves being ready to know and engage in having missed a piece of information or having missed asking a question that felt uncomfortable. It is looking for the missing information.
It’s the door to accepting or engaging in the dialogue.
It may be ok to accept that blame becomes the door opener, even if there are way better ones.
And yes, accountability is also about living up to the promises made. That is, the ones based on a common understanding.
The foundation of it all is having engaged in the relationship and putting the relationship first.