Clip / Education

Why a single brand-voice system prompt fails on turn 21

From Stop Writing Tone Instructions. Layer Them. - Isadora Martin-Dye, Isadora & Co · ≈0:57

Diagnoses the root cause of brand-voice drift in production chat agents: one prompt cannot simultaneously handle identity, situation, expression, and self-checking.

What’s in it

Diagnoses the root cause of brand-voice drift in production chat agents: one prompt cannot simultaneously handle identity, situation, expression, and self-checking.

Watch this moment

Clip transcript

is about that structure. The standard advice is write a detailed system prompt. Describe your brand's voice, give examples, and that does work for a while. It works for what I call the happy path. The happy path is every question that you have anticipated. You've given it examples, but turn 21 is the first one that the example didn't work. So, on turn 21, the model does something technically correct that your brand would just never say. It's not wrong exactly, but it's not you. This matters most where the voice is the product. Not for a product search on a retail site, but for a luxury hotel that spent 30 years building a specific relationship. A high-end real estate firm or in my case, a wedding venue. Places where a single wrong sentence can cost more than a refund. And the users are exactly the kind of people who notice. They're paying for a relationship and treating them like they won't is always going to backfire. Write in our brand's voice is a comment that says, "Just make it work." It does nothing that the model wasn't already going to try and do. And the reason it keeps failing isn't that the examples are bad, it's that you're asking one prompt to do four completely different jobs.