Most validation libraries make the same fundamental mistake: they assume your job is to judge whether data is good or bad, and then tell the user what went wrong. They're wrong about both parts. The Problem Nobody Talks About Let's say you're building a form. A user enters a phone number that's too short. A validation library fires back with an error message: "Phone number must be at least 10 digits". Now what? Your form renderer gets an error string and has to... guess what to do with it. Display it in red? Suggest padding? Disable the submit button? Hide the field? The library doesn't know. You have to write that logic yourself. But here's the real problem: the library threw away context . It knew: The input was a string It was too short The minimum length required The actual length Instead, you got a sentence. A string. And now you have to parse it back into facts to do anything useful with it. This happens everywhere. API validation. ETL pipelines. Data cleaning.…