8 AI prompts that turn a rough idea into a business case in under an hour
How to write a business case with AI
You’ve got an idea. You know it’s good. But every time you try to explain it to someone who matters, it falls apart. You ramble. They ask questions you can’t answer. The meeting ends with “let’s revisit this.”
The problem isn’t the idea. It’s that you’re trying to turn raw instinct into a structured argument in real time, which nobody can do well. What you need is a private pressure test before you’re in front of anyone.
This 8-prompt sequence walks your idea through the same gauntlet a sceptical investor or executive would put it through. Do them in order. By the end you’ll have a written business case, a one-paragraph pitch, and a clear picture of where your idea is strong and where it isn’t.
Prompt 1: The plain-English summary
What it does: Forces you to state your idea without jargon or hedging, in terms a non-expert can understand.
When to use it: Before anything else. If you can’t complete this prompt clearly, the idea isn’t ready.
You are a plain-language editor. I have a business idea I want to describe clearly. Ask me nothing. Take what I give you and rewrite it as a single paragraph of no more than 100 words. Use simple words. Remove all jargon, filler and vague language. Every sentence must say something specific. Here is my idea: [DESCRIBE YOUR IDEA IN YOUR OWN WORDS, AS ROUGH AS YOU LIKE]
How to use it:
Paste the prompt and dump your idea in the placeholder. Don’t overthink it.
Read the output. If anything still feels vague, run it again with that section rewritten.
Save this paragraph. It becomes the opening of your business case.
Example input: My idea is a subscription service for small restaurants that gives them access to a shared fleet of delivery drivers, so they don’t have to pay Deliveroo’s commission on every order.
What you’ll get: A tight, specific summary you can read aloud in 20 seconds without stumbling.
Advanced note: If the output is too generic, add one sentence to your input that says who this is specifically for and what they currently do instead of your solution.
That prompt alone will stop you walking into a meeting with a vague idea dressed up as a plan.
But one paragraph isn’t a business case. Subscribers get seven more prompts that take it the rest of the way:
Prompt 2 — The problem statement: Articulates exactly who has this problem, what they do instead, and what it costs them.
Prompt 3 — The market size estimate: Builds a TAM/SAM breakdown from your own numbers, with every assumption flagged.
Prompt 4 — The assumption audit: Lists what your idea depends on being true, ranked by how badly each one kills you if it’s wrong.
Prompt 5 — The unit economics model: Shows what needs to be true for the business to make money, under three growth scenarios.
Prompt 6 — The competitive position: Forces an honest look at existing alternatives and what it would actually take to beat them.
Prompt 7 — The devil’s advocate session: Ten sharp questions a sceptical executive would ask, with your weakest answers flagged.
Prompt 8 — The business case document: Assembles everything into a structured, shareable document, approximately 1,000 words.
Plus: the 8-prompt progress tracker to keep all your outputs in one place.