Your Agent Needs a Schema, Not a Better Prompt
LLM agents fail in production not from poor reasoning but from acting on domain-invalid states that prompts alone cannot enforce. A formal ontology using SHACL shapes defines machine-checkable rules—like "a refund must reference exactly one delivered order"—that validate agent actions deterministically in milliseconds without consuming tokens. This pattern separates flexible LLM understanding from rigid domain enforcement, turning validation rejections into structured feedback that teaches the agent or escalates to a human.