I've spent the last year building and running a SaaS almost entirely on AI-generated output — launch copy, code reviews, cold outreach, changelogs, support replies. Along the way I've written, tested, and thrown away something like 400+ prompts . About half of them are now in a curated pack I sell. The other half were just bad. This post isn't a sales pitch. It's the actual lessons from testing hundreds of prompts: why most of them fail, what a good one looks like, and how to test them syste...