Stuart Russell, Peter Norvig

1 card

1. 01

   An LLM agent is not a longer prompt but a loop: it perceives, decides, acts, then perceives the result of its own action.

   Artificial Intelligence: A Modern Approach · 1995

   An agent is a perceive–decide–act loop, and the guardrails sit on every turn.

   The textbook definition maps exactly onto what runs today: the sensors are the context (the user's message, files, tool results), the actuators are tool calls (search, run code, send an email). The loop closes when a tool result comes back into the context and the model chooses the next step. That is the difference from a chat call: a call never sees the consequence of its own action. Autonomy has a plain measure — how many turns the loop makes without a human. An agent is defined by its tools and its stopping rule, not by its model.

   “An agent is anything that can be viewed as perceiving its environment through sensors and acting upon that environment through actuators.”

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