Agency cold email that leads with a working prototype instead of a deck

The message

Hi [first name],

Rather than send a proposal, I built the thing.

Here's a working version of your booking flow, running in your browser. Real screens, real flow, not a mockup. Took an afternoon.

[link]

You can click through it and see whether the structure makes sense before we talk about money at all. If it's wrong, you've lost nothing and I've lost an afternoon.

If it's close, tell me what to change.

[your name]

Would you reply to this?