Sumanth (@Sumanth_077) “I built a Voice AI agent that books appointments over live phone calls! 100% ope” — TopicDigg

I built a Voice AI agent that books appointments over live phone calls! 100% open source. Runs on GLM-5.3 Flash through Telnyx, about $0.30 per booking call. The agent can handle the complete booking workflow during a real call: understand what the caller needs, check available time slots, collect the required details, book the appointment, generate a calendar invite, and confirm everything back to the caller. What makes this more than a simple voice chatbot is the tool layer behind the conversation. At the start of every call, the agent receives context like the current date, business hours, and available services. When the caller asks for a specific day or time, the agent checks the scheduling system and only offers slots that are actually available. Once the caller picks a time, it books the appointment, stores the details in a lightweight CRM, and generates a calendar invite. For the model layer, I used GLM-5.3 Flash through Telnyx Inference. It powers the agent during the call, and the same model is used after the call to turn the call summary into a personalized follow-up. GLM-5.3 Flash runs on Telnyx's own GPUs, so the open model is served directly through their inference infrastructure rather than adding a closed-model API markup on top. The overall flow looks like this: Caller → Voice Agent → Check availability → Book slot → Create calendar invite → Store CRM record → Generate follow-up GitHub: For the voice stack, I used Telnyx Voice AI. Telephony, speech-to-text, GLM-5.3 Flash inference, text-to-speech, and the agent itself all run through Telnyx with one API key and one bill, while the application handles the scheduling logic, booking tools, CRM, calendar invite, and post-call workflow. The scheduling layer is modular, so the same setup can be connected to Google Calendar, Outlook, Cal, or another booking system.