Lesson 2 of 5, 11 min with the exercise

Choose where AI belongs

Use AI only on the steps that need it.

Rules are cheap, fast and predictable, so use them wherever they work. If the invoice total is over a limit, a plain rule can route it.

AI earns its place on steps involving messy language or varied formats: reading an email to work out what the customer wants, or pulling fields from PDFs laid out in fifty different ways.

• Can you write the rule in one sentence? Use a rule.
• Does a person read and interpret something? AI might help.
• Would a wrong answer cause serious harm? Keep a person in that step.

See it in practice

Invented example, for a supplier invoice: reading fields from a PDF is an AI step. Checking the total against the purchase order is a rule. Approving a payment over the limit is a person. One process, three kinds of step, and only one needs a model.

Common mistake: Sending the whole job to a model in one big prompt. Split it up, so you can test each step and see which one failed.