construction of the task?

"Communicative games have a goal or aim that is not linguistic: successful completion of the game involves carrying out a task such as exchanging information.....in order to carry out this task it will be necessary to use language and by careful construction of the task, it is possible to specify in advance what language will be required."

What does "construction of the task" mean here?
Why does this make it possible to specify in advance what language will be required?
I don't understand what the last 2 sentences are talking about.

[Tdol]

The way the task is made- the sequence of steps, the details, etc. You build a task in such a way that you know beforehand what language will be required. A task involving buying a ticket, involves certain predictable steps, hence it is possible to anticipate the language that will be used.

[Eway]

So, it is saying that when the teacher is designing a certain task, he or she can know what words/sentences/grammar rules the students will be using when trying to complete the task? Is my understanding right?

[Tdol]

That's how I understand it.