I've only prompted so far, haven't filled yet, but I don't think writers should have to fulfill all requirements in a prompt, except maybe the big ones like not including certain squicks. At least I don't expect it when I post a prompt. Some of the highly specific details I see in prompts just seem superfluous. I can see how having specifics could help inspire some writers, but I can also see how it could discourage others. Personally I tend to go vague with my prompts when it's a rare pairing/trope/kink to increase the likelihood of someone taking interest.