An agent is an LLM that decides in a loop what action to take next, executes tools, observes results, and continues until a goal is reached. Not marketing — a specific architectural pattern. The definition matters because most 'agents' in the wild are workflows in disguise.
- 01State the agent definition precisely.
- 02Distinguish agents from workflows.
- 03Recognize the three canonical components.
The definition
Agent: an LLM in a control loop that (a) observes state, (b) plans an action, (c) executes it via tools, (d) observes the result, (e) decides whether to continue. The LLM controls the flow. In a workflow, the code controls the flow and the LLM completes fixed steps.
Why the distinction matters
Agents are flexible but unpredictable; workflows are predictable but rigid. Production systems usually mix: workflow at the top level, agents for the parts where flexibility is required. Calling a workflow an agent inflates capability claims and hides real design choices.
- Agents = LLM controls the loop; workflows = code controls the loop.
- Most production 'agents' are workflows with an agentic subroutine.