Skip to main content
Your agent speaks on behalf of your brand in every conversation, so getting the voice right matters. MerchantAI gives you direct control over how your agent sounds — from the overall personality down to how it handles specific topics. You can write a custom system prompt in plain English, start from a pre-built brand voice preset, set different response styles per topic, and test everything in the preview chat before a single real visitor sees it.

​
The system prompt

The system prompt is the core instruction set your agent follows. It tells the agent who it is, how it should communicate, what it should prioritise, and what it should avoid. You can edit the system prompt at any time from Configuration → Voice → System Prompt. When writing your system prompt, keep the following in mind:
  • Tone and language — Be explicit about how you want the agent to sound. Words like “warm,” “direct,” “concise,” or “approachable” carry meaning. If your brand uses British English, informal contractions, or specific terminology, say so.
  • What to prioritise — Tell the agent which topics it should handle confidently and which it should escalate immediately.
  • Things to avoid — List any phrases, claims, or commitments the agent should never make. For example, avoid making promises about delivery timescales that your logistics team hasn’t confirmed.
Use real language from your customer conversations when writing the system prompt. If your shoppers consistently ask “do you ship to X?” or “how long will it take?”, mirror that phrasing so the agent recognises and handles those queries naturally.

​
Brand voice presets

If you are starting from scratch or want a consistent baseline, MerchantAI offers a set of pre-built brand voice presets you can apply with one click. Each preset sets an initial tone and style in your system prompt, which you can then edit further.

Friendly

Warm, conversational, and approachable. Well suited for lifestyle brands, pet products, and consumer retail where a personal touch matters.

Professional

Confident, clear, and formal. Well suited for B2B, financial services, or any brand where authority and precision are important.

Concise

Short answers, minimal padding, fast to the point. Well suited for high-traffic stores where shoppers want quick, actionable information.
Presets are a starting point, not a constraint. After applying one, you can edit every part of the generated system prompt to match your exact requirements.

​
Per-topic routing rules

You can configure the agent to respond differently depending on the topic of a conversation. Per-topic routing rules let you define specific behaviours for categories of questions, separate from your general system prompt.
  • Billing and payments — Escalate immediately to a human; do not attempt to answer billing disputes or payment failures.
  • Product questions — Answer directly from the knowledge base; no escalation needed unless confidence falls below threshold.
  • Complaints and frustration — Trigger a handover to the human team whenever the agent detects negative sentiment or explicit dissatisfaction.
  • Competitor mentions — Decline to engage; acknowledge the question politely and redirect to your product’s strengths.
To add or edit routing rules, go to Configuration → Voice → Routing Rules. Each rule specifies a topic, a detection method (keyword, category, or model classification), and an action (answer directly, escalate, or apply a specific response template).

​
Previewing your voice

Before deploying any voice changes to live visitors, use the Preview chat in the dashboard to test your system prompt and routing rules. The preview chat runs against your live knowledge base and simulates the full agent behaviour, including guardrails and routing logic.
Send a variety of greetings, casual questions, and complex queries to check that the agent’s tone stays consistent across different types of interaction. Compare responses against your brand guidelines.
Voice customisation — including the system prompt, brand voice presets, and per-topic routing rules — is available on all paid plans. Free plan users have access to a default voice configuration only.