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Case study · July 4, 2026

Actively developed · still receiving updates

AI Voice Agent: Calls and Automatic Appointment Scheduling

AI phone agent that converses naturally, follows a sales script, and schedules appointments automatically. Custom architecture on Twilio with human-sounding ElevenLabs voice and an in-browser simulator to iterate the script before going to production.

TwilioElevenLabsLLMNode.jsVPS
AI Voice Agent: Calls and Automatic Appointment Scheduling

A phone salesperson that never sleeps

Voice agent designed for phone prospecting and appointment scheduling: it answers or initiates the call, converses naturally following a sales script, handles objections, and closes by booking an appointment on the team's calendar.

Custom architecture (no expensive middlemen)

  • Twilio ConversationRelay for telephony and voice streaming (STT/TTS managed by Twilio).
  • Own worker on a VPS running only the LLM logic: every conversation turn goes through the model with the canonical script and call context.
  • Human-sounding voice with ElevenLabs, integrated in both the real call and the simulator.
  • Key decision: going direct to Twilio instead of platforms like Vapi/Retell — per-minute cost rules once volume scales.

In-browser simulator

Before spending a cent on telephony, the script is tested in an in-browser call simulator: ringtone, real voice conversation (microphone + TTS), outcome and transcript at the end. Same script and same LLM as the real call — iterating the pitch takes minutes, not phone bills.

Everything measured

Every turn logs token usage and outcome (appointment booked, rejection, follow-up), ready to compute cost per minute and per appointment.

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