Chapter 5. The Four-Part Brief

The point

After this chapter you can write a brief: the message you send when you hand a job to an AI Worker. A good brief has four parts. It says what you want back (the outcome), in what shape (the format), from which sources (the inputs), and how far the worker may go without asking you (the autonomy). You also learn when to spell out steps, which source must win, and how to split a big job. And you learn to fix a brief one part at a time, match it to the task, and use one brief in Claude and in ChatGPT.

Why it matters

Brightline Wholesale Supply, the book's example company, pays its suppliers' bills once a week, on Friday. The payment run is the list of bills to pay that day. Brightline's AP Worker gets the run ready. AP means accounts payable, the bills a company owes.

On Monday, October 19, Dave, the controller who runs Brightline's accounting, sent the AP Worker one line before a meeting: "Get this week's payment run ready. Everything's in the AP folder." The folder held the list of 15 open invoices, the ones not paid yet. It also held the vendor records (each supplier's payment terms), the approvals log (every approval so far) and the text of one Tri-County Freight invoice. And it held two versions of the AP policy, Brightline's rules for paying bills. Version 3 is the current one. The other is an old, retired copy of version 2.

The answer looked well organized. It had four problems.

• It did a different job. It proposed paying all 15 invoices. This week's run was set for Friday, October 23, so Dave meant only the bills due by the next run, on October 30. Five were due later.
• It came back in the wrong shape. It was two pages of paragraphs. Maria, the office manager, needed a file she could check row by row. To get one, she would have to type every row again.
• It used the wrong source. It said Midwest Packaging's $6,480 invoice did not need Dave's approval, because only invoices over $10,000 did. That was the old rule, in version 2. Version 3, approved on September 1, lowered the limit to $5,000. The worker read both files and picked the old one.
• It decided something nobody asked it to decide. One invoice, from Northern Maple Paper, was in Canadian dollars. The worker found an exchange rate online, converted the amount and added it to the run. The policy says nothing about foreign currency, so the worker filled the gap with its own guess.

Maria tried again, with fourteen numbered steps. Step 2 said to work out each due date from the payment terms printed on the invoice. But Lakeshore Janitorial's invoice still showed its old terms, Net 45, which means pay within 45 days. The vendor record says Net 15, and the policy says the vendor record wins. So invoice 5131 was due on October 15, and it was already late. Step 2 made it look due in November, so it was left out of the run. The worker followed her steps perfectly, mistakes included.

Neither message was a good brief. Dave said too little, so the worker guessed four times. Maria spelled out every step, including a wrong one, and never said what she wanted back. A good brief sits between the two. It says clearly what you want, but not every step to get there. The next page shows a brief that would have worked.