I Think “Agent” May Finally Have a Widely Enough Agreed Upon Definition
Source: https://simonwillison.net/2025/Oct/20/agent-definition/ Author: Simon Willison Date: 2025-10-20
Summary
Simon Willison argues that the term “agent” has finally reached enough consensus to be useful. Proposes a working definition and explains what separates agents from LLM-powered features.
Key Claims
- Working definition: an agent is “an LLM that is placed in a loop with tools, where its outputs from one iteration can inform the next.”
- Key criterion: the loop. A one-shot LLM call is not an agent, even with tools. An agent is defined by iteration and self-direction.
- What makes it an “agent”: the model can decide to take additional steps, use tools, and revise its approach based on results.
- Willison’s concern: “agent” is still applied too broadly — automations that use LLMs but don’t have real autonomy get called agents.
- Practical threshold: an agent can meaningfully “get stuck” and require recovery logic. A simple LLM call cannot.
Entities
Concepts
- Coding Agents — definitional clarity for what agents are
- Autonomous Research — autonomous = agents