The system prompt is the single most important thing you'll write for your agent. It's the master set of instructions that determines how your agent thinks, speaks, and behaves on every call. A great system prompt makes the difference between an agent that occasionally frustrates callers and one that genuinely impresses them.

What a system prompt is

Think of the system prompt as the briefing you'd give a new member of staff on their first day. You'd tell them: who the company is, what you do, how to handle common situations, what to say when they don't know, when to escalate, and how to close a conversation politely.

Your agent reads this briefing before every single call and uses it to guide its responses. It doesn't just repeat it word-for-word — it uses the instructions as a framework to handle whatever the caller says.

Where to find it

Go to Agents → Edit → Agent Setup. The system prompt field is the large text area at the top of the tab. After making any changes, click Sync to Voice Agent to push them live.

voiceforge.pro/agents/agent_xxx — Agent Setup
Agent Details
Training Material
Agent Setup
Telephone
System Prompt
🔄 Sync to Voice Agent

The structure of a good system prompt

A well-structured system prompt has six sections. You don't have to use exactly this structure, but it's a reliable starting point:

## Identity Who the agent is and who it works for. ## Role & Responsibilities What the agent is there to do on every call. ## Services & Knowledge What the business offers — key services, prices, areas covered. ## Call Handling Rules How to handle different call types — bookings, enquiries, complaints, emergencies. ## Data Capture What information to always collect from every caller. ## Closing the Call How to end every conversation politely and positively.

A real example — plumbing business

Here's a complete, production-quality system prompt for a plumbing business. Use this as a template — replace the details with your own:

## Identity You are Jordan, the AI voice agent for Acme Plumbing Services — a trusted local plumbing company serving Durham, NC and surrounding areas. You speak in a warm, confident, professional tone. ## Your Role You answer every inbound call, understand what the caller needs, capture their contact details, and ensure they feel confident their issue will be handled promptly. ## Services We Offer - Emergency repairs (leaks, burst pipes, no hot water) - Boiler servicing and installation - Bathroom and kitchen plumbing - Drain unblocking - New builds and renovations We serve Durham, Chapel Hill, and Raleigh. We do NOT cover Charlotte or Greensboro. ## Call Handling EMERGENCY (gas leak, flooding, no heat in winter): Express urgency, assure callback within 30 minutes, capture name and number immediately. BOOKING REQUEST: Capture name, number, address, job type, and preferred time. GENERAL ENQUIRY: Answer using your knowledge. If unsure, capture details and promise a callback. COMPLAINT: Listen fully, apologise sincerely, and always escalate to a callback. ## Always Capture - Full name - Best phone number - Address or postcode - Nature of the problem - Urgency level (emergency / urgent / routine) ## Closing Every Call Confirm what will happen next ("Someone from our team will call you back within the hour"). Thank the caller by name. End warmly.

Key rules for great system prompts

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Be specific
Don't say "handle emergencies professionally." Say "For gas leaks: express urgency, assure callback in 30 minutes, capture name and number immediately."
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Define the limits
Tell the agent what it doesn't do. "We do not quote prices on calls — always direct to a callback." Undefined limits lead to hallucinated answers.
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Always include data capture
List exactly what information to collect. Name and number at minimum. Add address, job type, and urgency for most service businesses.
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Define the tone
"Warm but efficient." "Professional and reassuring." "Friendly and energetic." One sentence of tone guidance shapes every response.
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Don't write a novel
500–1000 words is ideal. Much longer and the agent may lose focus. Use bullet points for lists, not paragraphs.
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Don't leave edges undefined
What happens if someone is abusive? If they ask a question completely outside your services? Plan for edge cases — they will happen.

Iterate based on real calls

Your first system prompt won't be perfect — and it doesn't need to be. The best prompts are refined over the first two to four weeks of live use. After every few days of calls, read through the summaries and ask:

  • Did the agent fail to capture information it should have?
  • Did it give an answer that was incorrect or off-brand?
  • Did it handle any call type awkwardly?
  • Were there call types that weren't covered in the prompt at all?

Add instructions to handle each gap. Sync. Repeat. Most agents reach a very high quality standard within 2–3 weeks of real-world refinement.

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Use Test Mode after every prompt change
After editing your system prompt, always use Test Mode to verify the change worked as intended before real callers experience it. Takes 2 minutes and catches most issues before they reach customers.