HangON: Voice Front Desk for Solo Trades

Solo tradespeople lose jobs every day because their hands are busy when the phone rings. A caller with a leak won't leave a voicemail; they call the next number. HangON is a voice front desk that answers for them. The call runs on AssemblyAI's Voice Agent API: speech to text, the LLM and the voice over a single WebSocket, with barge-in and adaptive turn detection. We use balanced mode so callers who pause mid-thought ("Tuesday... actually, no, Wednesday at 2") can finish before the agent replies. The agent acts through client-side tool calls. check_calendar_availability tests the caller's requested time against real booked jobs and business hours and returns genuine open slots if it is taken. book_service_appointment saves the job to Postgres only after the agent reads it back and the caller says yes. send_confirmation_email sends the confirmation through Resend from our own domain, after the agent asks for the address and confirms the spelling. AssemblyAI's LLM Gateway turns the live transcript into structured job fields with a strict JSON schema; anything the caller never said stays empty instead of being guessed. After the call, the same gateway writes the technician a brief: the problem, the caller's mood, and parts to bring. Our server mints a short-lived voice token for each call, so API keys never reach the browser. HangON is built to be honest: no placeholder data, no false success messages, and clear errors instead of canned answers.