Start here. This is the direct spoken answer to practice first.
Overview
Using an LLM inside a workflow does not automatically make the system an agent.
In a deterministic workflow, application code chooses the steps and transitions, even if one step calls a model. In an agent, the model helps decide which action or tool to use next and when the task is complete. I use that flexibility only when the task cannot be expressed clearly enough as a fixed flow and the actions can be safely bounded.