At my workplace, we face a challenge in that "agile" too often has meant "vague requirements, bad acceptance criteria, good luck!" We're trying to address that, as a general improvement effort. So, as part of that, I am proposing that we generate design documents that, above and beyond the user story level, accurately reflect the outcome of preliminary investigations of the effect of a given feature within the system and including answers to questions that we have asked the business.

Is there an effective standard for this? We currently face a situation where a new feature may impact multiple areas in our "big ball of mud" system, and estimates are starting to climb due to this technical debt. Hopefully more thoughtful design processes can help.