[sailfast]

Many people have said this but here goes anyway: The tooling will not help you better define the specifications. The tooling will not help you manage changing specifications. You can cover all the bases easily in a free Github project (Edit: pick your web-based tool, basically) without too many issues.

I would argue that the reason things get called out as poorly defined or change is because risks are not addressed early, and hypotheses are assumed to be theorems.

Make sure your teams test the main assumptions early, with actual code if at all possible. That will call out why your stories aren't clear enough.

Tools are useful, but they won't solve your problem.