That depends very much on which of the dozen+ definitions of "agent" you are using.

I think Anthropic does a good job of nailing it down to two definitions, one of which is very commonly referred to as agents but more appropriately called _workflows_, and this is the vast majority of what you'll see in the wild.

https://www.anthropic.com/engineering/building-effective-age...

agents are just the rebranded version of automated workflows and sometimes its an LLM doing the validation