If you’re willing to defer many of the refined decisions about product capabilities and characteristics to the developers, you can write less requirements documentation. This can also work if customer representatives are available to work with developers to pin down the specifics and make the necessary decisions at construction time.

However, if your key stakeholders need a shared expectation of what will be delivered, consider producing a more complete specification.

As usual, you need to balance cost and risk. Scanty or verbally communicated requirements cost less than if you write requirements in greater detail, but they do pose some risks.