How to Validate a Business Idea With Gemini (8 Prompts + 1 Gem)

Most Idea Validation Is for Show. This One Actually Checks.

I’ve killed more projects at the idea stage than most people start. That’s not a boast. It’s the reason I still have time and money.

The problem with a new idea is that it arrives fully dressed. You see the finished newsletter, the packed launch, the nice round subscriber number. You do not see the six months of grinding out content nobody reads. The gap between those two pictures is where I’ve lost the most.

So I built a gate. Eight prompts I run before I let myself fall in love. I run them in Gemini, not ChatGPT, and there’s a specific reason for that, which I’ll get to. The short version: Gemini can actually go and check whether the world agrees with me, and I’ve stopped trusting any idea validation that can’t.

Here’s the whole thing.

Why Gemini for this

Most idea-validation prompts are for show. You describe your idea, the model tells you it’s promising, you feel good, you build it, and it dies. The model was never checking anything. It was pattern-matching your enthusiasm back at you.

Gemini’s free tier does two things that break that loop. Its answers are grounded in Google Search, so when I ask whether a market exists, it goes and looks rather than guessing from training data. And Deep Research will spend a few minutes crawling dozens of pages and hand me back a proper report. Free accounts get a handful of those a month, which is plenty when you’re only running it on ideas that survive the first few prompts.

There’s also Gems, which are custom saved assistants, free for everyone now. I’ve turned this whole sequence into one. More on that at the end.

The point of grounding is simple. I don’t want a model that agrees with me. I want one that can be sent to find out I’m wrong.

The eight prompts

Run them in order. Each one is allowed to kill the idea. If it does, you stop, and you’ve saved yourself a season of work.