Automation repeats a sequence you defined. An agent is given a goal and works out the steps itself.
If the process is identical every time, a script is cheaper, faster and far easier to debug. Do not over-engineer it.
When inputs vary and the path changes case by case, a script breaks. That is where autonomy earns its cost.
Agents make mistakes. If a mistake is cheap to reverse or a human reviews it, autonomy fits. If not, it does not.
Including when the answer is a simple script rather than an agent.