3.1 One rhythm in three parts

In everyday life. You hire a painter. You choose the colors and say which rooms, and you agree that you will walk through the rooms before paying. Then you go to work, and the painter paints the rooms. When you come home, you check the edges and the trim around the doors and windows, and only then pay.

At work. Dave (the controller who runs Brightline's accounting) gives the company's AP Worker one task: reconcile a vendor's statement, and change nothing. He should let it work, then read what comes back before he closes September's accounts.

The book's operating rule has three parts: Humans define intent. AI Workers execute. Humans verify outcomes. With the painter, you define the intent, the painter executes, and you verify the outcome. The 10-80-10 rhythm is that rule with numbers added. The human defines the first 10 percent, the worker executes the middle 80, and the human verifies the final 10.

The pattern is older than AI. It is often credited to Steve Jobs, and the entrepreneur Dan Martell describes it the same way. In this pattern, you spend the first 10 percent of a project setting the vision (the outcome you want). A capable team does the middle 80. Then you return for the final 10 to refine and approve.¹ The first edition of this book applied it to AI, with AI Workers in the place of the team. Nothing else had to change.

The table below shows the three parts. The next three pages explain each part and the words in its row.

Part	Who leads	What happens	What it produces
First 10 percent	The human	Intent, scope, authority and the review contract are set	A brief the worker can act on alone
Middle 80 percent	The worker	The worker plans, uses its tools and does the work	The output, plus the evidence the contract asked for
Final 10 percent	The human	Evidence is reviewed, the output corrected, then approved or sent back	A decision, and work that may leave your hands

(The review contract is how you will know the work is right, agreed before it starts.)

Figure 3.1. The 10-80-10 rhythm. The human owns both ends. The worker owns the middle.

Important

A shape, not a timesheet

Read the numbers as a shape, not a timesheet. They describe who leads each part of the work, not minutes on a clock. The first time you delegate an unfamiliar task, both ends take longer: you write the brief with care and check the result line by line. A task that has run without errors every week for months may need five minutes of setup and a quick look at its evidence. The split of responsibility stays fixed while the minutes change.

The two ends belong to a person, because judgment, values and accountability cannot be handed over. (Accountability means the work goes out under your name.) The middle belongs to the worker, because that is where execution scales (the work can grow without taking more of your time).

The rhythm is also why this book teaches you to manage an AI Worker before it teaches you to build one. The skills that matter at both ends are defining work well and judging it well, and every route through the book needs them.

Check yourself

In the 10-80-10 rhythm, who leads the middle 80 percent?

Sources