Prompt, Workflow or Agent

An agent is a model using tools in a loop, choosing its own next step. Most jobs don't need one. A single good prompt, or a fixed sequence of prompts, is faster, cheaper and easier to check, so the first question for any job is which of the three it needs.

When a job does need an agent, most of its mistakes can be fixed around the model, in the harness: the instructions, tools, limits and checks you control.

The running example

A help-article assistant drafts and updates a software product's help articles from product notes, follows a style guide, and must never publish on its own.