Numbers in AI-built decks should come from the source, not the model

A wrong number in front of a client or a board costs far more than the time it took to make the slide. Before AI, the main risk was a copy-paste slip between Excel and PowerPoint. Now there is a second way for a figure to go wrong: it can be retyped, rounded or regenerated somewhere between the model and the slide.

The answer is not to keep AI away from the deck. It is to be clear about which job belongs to whom.

Let AI decide what to show

AI earns its place in the analytical part of the work: reading a model or a report, suggesting the storyline, choosing the comparison that makes the point and drafting a message title for each chart. That is judgment and language, and today's models are strong at both.

Let the data supply the numbers

The figures themselves should come from where they are maintained, which is usually an Excel model. There are three practical reasons:

• Checking. A reviewer can trace a figure back to a cell instead of asking how it was produced.
• Updating. When the model changes, linked charts refresh from the source. Nothing is regenerated, so nothing new can slip in.
• Cost. Refreshing a linked chart does not involve the model, so it spends no tokens.

A simple test for every chart

Before a deck goes out, ask three questions of each chart:

1. Where did these numbers come from, and can I open that source?
2. If the source changes tomorrow, how does this chart get updated?
3. If I change the sort order or a label, do the values stay exactly as they were?

If the answer to the first question is "the AI wrote them", treat the chart as a draft.

What this looks like in practice

Take a month-end pack built from one Excel model. Your AI proposes the storyline and the chart for each slide, and the charts are linked to ranges in the model. When finance posts a late adjustment, the analyst updates the model, refreshes the deck and reviews what changed. The AI then revises the commentary where the story moved. The numbers never pass through the model's text.

The same rule holds for deal work. When the valuation model changes the night before a deadline, every linked chart follows it, and every number in the deck still ties out to the model.

How Grunt keeps the numbers right

In Grunt, charts and tables can be linked to Excel ranges in local workbooks or in SharePoint and OneDrive, and refreshed in one click. When you save the workbook, Grunt tells you fresh data is available and you choose when to update the slide. The Data Editor shows the data behind every chart, and values you change by hand keep their source value, so you can reset them at any time.

AI decides what to show. Grunt keeps the numbers right.

See how Excel connections work in Grunt for PowerPoint →