A guardrail that only knows categories can label a problem. It can't reason about one. The bouncer who never read the guest list Most guardrail tools look the same: categories (content safety, PII, prompt injection), a detector for each, and a threshold. Cross it and you're blocked. That's a taxonomy . It answers "which bucket does this belong in?" You need one, but a lot of teams (me included, a while back) treat the buckets as the whole safety system. An ontology a...