We turn down three kinds of work, and saying so early has saved everybody involved a great deal of time.
The first is anything where the process has never been run manually. There is nothing to observe, so there is nothing to describe, and what gets built is a guess with a maintenance cost attached.
The second is work where the person doing the step has not been told it is happening. That is not a technical constraint, it is the difference between a build people use and a build people route around.
The third is anything that must be finished before a date nobody has justified. Deadlines are fine. Undiscussed deadlines are a signal that the scoring conversation has not happened yet, and we would rather have it now than in the second week.
