With Agile, everything is transparent… as such, it will be very hard to cover up incorrect expectations that you establish with your customer.
Therefore, with regards to correct expectations, it is wise to keep things — work, dependencies, risks, impediments– visible and open for inspection.
Then we can work closely with the customer during development based on what’s really happening — not spending time to cover up — and adapt accordingly.
No surprises … the customer must collaborate with developers because everything cannot be known in advance … there will be tradeoffs to be made.
Establishing an open and honest relationship with the customer is the most important aspect of Scrum.