Ask HN: Do you have a spec?

Our product team struggles to clearly define and communicate product requirements as they change. This trickles down into unclear specifications for our engineering team.

We've used Confluence to try and gather requirements and track changes with limited success.

Anyone have any useful tools, processes or tips that they can share? How do your teams collaborate on functional specs? Do you write use cases "As a, I want, so that?"

Thanks!