I said AI can’t simulate your customers. Then I built a tool that does.

Sort of. Would you like to be insulted and advised at the same time?

A few months ago, I wrote that AI cannot simulate your customers’ behaviour. LinkedIn was buzzing about a research paper claiming LLMs could reproduce human purchase intent, and founders everywhere were salivating at the idea of never having to talk to a real person again.

My take was simple: no. LLMs match semantic patterns. They don’t simulate intent. They can’t tell you whether Sarah from accounting will upgrade to Enterprise because her boss just got budget approval and she’s tired of exporting CSVs manually. That’s behavior. That requires context; no model has.

I still believe that. Every word.

And then I built a tool that spins up 5 virtual customers and lets them roast your website.

It’s seriously a bit offensive. But also useful according to one of my testers:

Thanks V. :D

Wait, what?

Roast-my-website-

It’s called RoastMyWebsite. You paste in a URL of your homepage or someone else's (don’t you dare paste mine in, it’s perfect). The tool scrapes your homepage (and pricing page if it finds one), generates 5 realistic ICPs with different roles, company sizes, skepticism levels, and technical backgrounds, and then simulates each of them visiting your site for the first time.

They have 47 tabs open. They’re impatient. They’re real in the ways that matter for this specific job.

The output: a grade, a bounce rate, 5 specific insights quoting your actual copy, and a pre-written LinkedIn post you can pretend you wrote yourself.

Try it yourself: https://tear-my-site-down.vercel.app/ (yeah it’s free)

So which is it, Leah?

Here’s the distinction that matters.

What AI can’t do: simulate real customer behavior over time. Predict churn. Model willingness to pay. Understand the political dynamics inside a buying committee. Replace talking to your actual customers.

What AI can do: evaluate whether your messaging is clear to someone seeing it for the first time. Spot contradictions between what you say and what you signal. Tell you that your homepage says “simple” four times but your pricing page has 47 line items. Flag that your CTA says “Get Started” but clicking it opens a 12-field form.

The first is behavior simulation. The second is heuristic evaluation. They’re fundamentally different jobs.

Heuristic evaluation doesn’t need to “know” your customer. It needs to read your page with fresh eyes and notice what’s confusing, contradictory, or missing. That’s pattern matching, and pattern matching is exactly what LLMs are good at.

Why this works (and where it doesn’t)

The tool generates 5 personas with different contexts: a junior PM at a startup, a VP Engineering at an enterprise, a price-sensitive founder, a non-technical head of ops, a skeptical CTO. Each one gets a gut reaction, a confusion point, an objection, and an action (sign up, keep reading, or close the tab).

Where it’s genuinely useful:
- Catching messaging blind spots you can’t see because you wrote the copy
- Stress-testing your homepage against different audience segments simultaneously
- Getting a fast read on whether your positioning lands before you spend money driving traffic
- Generating specific, quotable feedback (not “improve your CTA”)

Where it falls apart:
- It can’t tell you if people will actually buy
- It doesn’t know your market, your competitors’ latest move, or your pricing conversation
- The personas are plausible, not real. They’ll never surprise you the way a real customer interview will
- If your site is genuinely bad, you don’t need AI to tell you that

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If you want to roast my roasting tool back, do it in my chat :D

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The meta lesson

The debate about AI and customer simulation is a false binary. It’s not “AI can simulate customers” vs “AI can never be useful for understanding customers.”

The useful frame is: what job are you hiring AI for?

If the job is “tell me what my customers will do next,” AI will fail you. If the job is “give me 5 fresh pairs of eyes on my homepage in 60 seconds,” it’s shockingly good at that.

Know the difference. Use both.

Try it: https://roast-my-site-leah.vercel.app/

Good to be back, I’m sorry for what the app does.

But at least it’s useful.