How to write your AI voice agent's script in 30 minutes
You don't need a consultant to write your AI voice agent's prompt. Here's the 5-block canvas that covers 90 % of calls — and the 3 mistakes that make an agent bad in production.
The 'system prompt' of your AI voice agent is the one document that decides its quality. Many agents fail because that document is either 2 lines or 12 pages. The effective shape is 5 blocks and takes 30 minutes.
Block 1 — Identity#
One sentence. "You are Yasmine, [company name]'s voice assistant. You answer inbound phone calls." No novel, no elaborate personality — just who's speaking and what for.
Block 2 — Mission#
- 3 to 5 action verbs max.
- "You book appointments, share opening hours, and transfer emergencies."
- What the agent does NOT DO should be just as explicit. Example: "you never quote an exact price."
Block 3 — Tone#
One sentence. "You are warm, concise, and never use more than 2 sentences per turn." That last point matters: chatty agents get hung up on.
Block 4 — Business rules#
Your specific constraints. "For a booking, ask: name, phone, short reason. Never offer before 9am or after 7pm. If Saturday request: transfer." A bullet list, 5 to 10 lines max.
Block 5 — Available tools#
List the functions the agent can call: `check_calendar_availability(date, duration)`, `book_appointment(name, phone, slot, reason)`, `transfer_call(number, reason)`. One line per tool plus a 5-word description.
The 3 mistakes to avoid#
- Giving full sample dialogues — the agent parrots them verbatim instead of reasoning.
- Writing "be professional." Too vague, the LLM has nothing to act on.
- Forgetting the fallback: "if you don't know, simply say 'I'll pass this on, we'll call you back.'"
With this canvas, you write your prompt in 30 minutes and iterate after 50 calls. VocazAI ships a sector-specific template — first month free to calibrate.