The two failure modes
When teams train an AI agent for the first time, the output usually falls into one of two failure modes:
- The "generic LLM" voice — overly polite, hedged, full of "I understand", uses bullet points where humans would write a sentence. Sounds like a chatbot.
- The "Slack DM" voice — too casual, drops articles, makes jokes that don't land. Sounds like an intern.
Neither sounds like your brand. The fix is not "tweak the prompt" — the fix is to give the agent the same materials a new hire would read on day one.
The voice triangle
Every brand voice can be expressed as three coordinates:
- Warmth — formal ↔ warm
- Pace — careful ↔ direct
- Register — corporate ↔ playful
Pick a point. Write five lines that hit that point. Those five lines become your voice anchors. The agent will weight everything else against them.
What to actually feed it
In order of importance:
- Five exemplar replies — actual messages your best teammate sent, with the customer context redacted. These are worth more than 200 pages of style guide.
- One "do not say" list — phrases, words, formatting habits the agent should never use. ("Unfortunately" is on most teams' list. So is the em-dash, on others.)
- Your top 20 cited answers — for the most-asked questions, write the answer you wish a teammate would send. Lock it in as canonical.
- Policy & product docs — for the long tail. The agent should ground here, not invent.
What not to feed it
- Marketing copy. The voice on a landing page is not the voice in a support reply.
- Old chatbot scripts. They will leak through.
- Slack threads. Internal jargon will leak through.
- The CEO's tweets. They were not written to a customer in distress.
The weekly tune
Once a week, pull the bottom 10 replies (by CSAT or by the agent's own confidence score). Look at them in plain text. Ask "would I send this?" If no, find the source it was grounded in and rewrite the source. The agent is downstream of your knowledge. Fix the knowledge.
Six weeks of that and the agent sounds like you — because it is, structurally, you.