Most people think AI receptionists are just chatbots on the phone. They're not. Here's the actual stack behind a real AI voice agent: → LLM APIs — the brain. GPT, Claude, Gemini — this is where the actual thinking happens. → Retell AI — handles the live phone call. Listens, responds, books. No human needed. → n8n — connects everything. If Retell is the person talking, n8n is the one actually doing the work behind the scenes. → Google Calendar — appointments land here automatically. Zero manual entry. → Google Sheets — lightweight CRM for call logs, lead data, client records. Five tools. One system. Infinite calls. This is the stack I'm learning to build real AI agents on. Follow Krittiya Clark —I document every build.