Which one-sentence distinction is most accurate?

Answer: The model is the brain, the tool is the wrapper, and the agent is the system

The model is the brain, the tool is the wrapper, and the agent is the system ✓ — Correct! This is the cleanest mental model: the model is the brain that reasons, the tool is the wrapper and workflow that makes the brain usable, and the agent is the system that connects that brain to memory, channels, tools, and actions that complete work in the real world.

They are just three names for the same thing — Wrong. These three ideas are tightly related, but treating them as synonyms makes it impossible to understand why the same model can feel weak in one product and powerful in another.

The model is the UI, the tool is the data, and the agent is the chip — Wrong. UI, training data, and chips belong to entirely different layers. They matter, but they are not the three layers this batch is trying to separate.