Voice AI7 min read

    Voice Agent for Booking Appointments — Ready-to-Deploy Template

    A complete, configurable voice AI template for automating appointment scheduling via phone. Covers system prompt, calendar integration, confirmation flow, and edge cases.

    H
    Hestur AI
    hestur.co
    2–3 days
    Setup Time
    with API access ready
    24/7
    Calls Handled
    no hold times, no missed calls
    95%+
    Booking Accuracy
    with structured calendar data
    $0.40–0.80
    Cost/Call
    at avg 3-min booking call

    What This Template Covers

    • ✓Ready-to-use Vapi assistant configuration (JSON)
    • ✓System prompt template — fill in your business details
    • ✓Calendar tool call spec (Google Calendar / Acuity / Jane)
    • ✓Confirmation + reminder SMS workflow
    • ✓Cancellation and reschedule handling
    • ✓Edge case handling: no availability, special requests, new vs existing client

    System Prompt Template

    // Replace [BRACKETS] with your business information

    You are [AGENT_NAME], the booking assistant for [BUSINESS_NAME].

    Your job is to help callers schedule, reschedule, or cancel appointments.

    // Services and availability

    Services offered: [LIST_SERVICES]

    Hours: [DAYS_AND_HOURS]

    Location: [ADDRESS]

    // Behaviour rules

    - Keep responses under 2 sentences.

    - Always confirm: service, date, time, and caller name before booking.

    - If no slots available in preferred window, offer next 3 available.

    - If caller has a medical/complex question, transfer to staff immediately.

    // Escalation

    Transfer trigger: "urgent", "emergency", "complaint", "not happy", 3rd attempt fails.

    Booking Conversation Flow

    1
    Greeting (3 seconds)
    "Thank you for calling [Business Name]. I'm [Name] and I can help you book an appointment. Are you a new or returning patient/client?"
    2
    Identify the service
    "What type of appointment are you looking for?" → Match to service list → Confirm duration.
    3
    Offer availability
    Call calendar API with `getAvailability(service, preferredDate)` → Return 3 nearest slots → "I have [Day] at [Time], [Day] at [Time], or [Day] at [Time] — which works best?"
    4
    Capture details
    Name (first + last), callback number (confirm it), any notes for the practitioner.
    5
    Confirm and book
    Repeat back: service, time, date, name. "Can I confirm — [Service] on [Date] at [Time] for [Name]?" → On YES → call `createAppointment()` → Send confirmation SMS.
    6
    Close
    "You're all set. You'll get a text confirmation shortly. Is there anything else I can help with?"

    Calendar Tool Call Spec

    ToolInput ParametersReturns
    getAvailabilityservice: string, date: ISO string, range: number (days)Array of available slots [{start, end, staffId}]
    createAppointmentservice, start, clientName, clientPhone, notesappointmentId, confirmationCode
    cancelAppointmentappointmentId, reasonsuccess: boolean, nextAvailability
    rescheduleAppointmentappointmentId, newStartnewAppointmentId, confirmationCode

    Post-Call Automation

    • ✓Vapi call_ended webhook → extract: appointment ID, client name, phone, booking status
    • ✓If booked: send SMS confirmation "Your [service] is confirmed for [date] at [time]. Reply CANCEL to cancel."
    • ✓24h before: reminder SMS "Your appointment is tomorrow at [time]. Reply CONFIRM or CANCEL."
    • ✓2h before: final reminder SMS with address/parking info
    • ✓If no-show: send reschedule link within 30 minutes
    • ✓Push appointment data to CRM contact record (new contact if first booking)

    Edge Cases to Configure

    Edge CaseAgent Behaviour
    No availability in next 7 daysOffer waitlist — "Can I add you to the waitlist? I'll text you as soon as a slot opens."
    Caller wants specific practitionerFilter getAvailability by staffId — if no slots, offer next available
    Caller unsure which service they needOffer brief description of each, transfer if complex medical question
    Caller wants to reschedule same-dayCheck cancellation policy, proceed if allowed, flag same-day in notes
    Non-English caller detectedIf multilingual configured: switch language. If not: transfer immediately.

    Deployment Checklist

    • ✓Replace all [BRACKETS] in system prompt with business information
    • ✓Test getAvailability with a real date — confirm it returns expected slots
    • ✓Test createAppointment — confirm it appears in the calendar
    • ✓Test SMS confirmation — confirm it sends within 30 seconds of booking
    • ✓Make 10 test calls covering: normal booking, no availability, cancellation, reschedule, transfer trigger
    • ✓Shadow mode for 3 days before going live
    Don't skip the cancellation policy step. Build in: cancellation window (e.g., 24h notice), whether late cancellation triggers a fee, and what the agent says when a caller tries to cancel within the no-cancel window. Handle this in the prompt explicitly — agents that don't have rules here will apologise and still cancel the appointment.
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