Models don't have agency, systems do: how shaped tokens become function calls

sethjuarez · x · 2026-09-29

Seth Juarez's essay "Models Don't Have Agency. Systems Do." dissects where agentic behavior actually comes from.

Core claim: an LLM only emits tokens — it originates no intent and performs no action, so by the philosophy-of-action definition it has no agency. The runtime built around it does.
Mechanism: when a model says "Sure, I can help you book a flight to Tokyo Tuesday afternoon," a human can act on it but a program chokes — the words are there, the shape is not. Shaping output as a function call ({ name: "bookflight", ... }) lets the runtime execute the real function; the model still only made text.
He lays out a progression from word to structure to function: closing the gap by constraining what the model is allowed to say, not by making it smarter — that's what hands agency to the system.

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