THE PRACTICAL TAKEAWAY

Use a defined sequence when the path is predictable. Consider an agent only when the task needs flexible choices and you can test its limits.

Separate the destination from the route

A workflow follows a route you define. An agent can make choices about the next step and which tools to use. Anthropic uses this distinction in its guide to building effective agents. The difference matters because each additional choice expands what you need to test.

If your process always extracts details, checks a rule, and prepares a draft, a fixed sequence may be sufficient. If it has to explore an unfamiliar problem and decide what evidence to gather next, a more flexible system could be useful.

Price the extra freedom

Autonomy has operating costs beyond a model bill. Someone must define permissions, review unusual behaviour, maintain tool connections, and investigate failures. A system that makes more decisions may also need more steps to finish the job.

Write a permission list before a prompt: what can it read, what can it change, and what requires approval? For an early pilot, prefer read-only access and draft outputs. Give every run a time or step limit and a clear route back to a person.

Earn complexity with evidence

Build the simplest version that can attempt the job. Test it on representative examples, including missing information and conflicting instructions. Record where a fixed route fails and why. Add flexibility only when it addresses a demonstrated limitation.

Do not choose an agent because it looks more advanced in a demo. Choose it when a measured improvement outweighs the additional monitoring and maintenance. The right architecture is the one your team can operate reliably after the launch excitement fades.

Source & further reading
Anthropic: Building effective agents
Background reading on the distinction between predefined workflows and model-directed agents. Our decision checklist is an editorial application, not a vendor benchmark. Reviewed 5 October 2026.

ModelMillionaire publishes AI-assisted editorial guidance. Examples are illustrative unless explicitly identified as documented cases. Our editorial approach.