Hey Fatima, we actually build and deploy these for HVAC and similar businesses, so I'm happy to share what works in practice On architecture a strong system prompt beats structured flow for HVAC; calls are too unpredictable to lock into a rigid path. handle bookings, inquiries and emergencies in the prompt with clear instructions for each scenario On stack, retell alone is enough to start. Only bring in n8n when you need to push data somewhere like a CRM or Google Sheets. don't add tools you don't need yet For HVAC clients, the only three things they actually care about are does it answer every call, does it book the job, and does it sound professional? that's it Minimum to start selling: working agent, a number, and one clean demo call recording. that's all you need for the first client full workflow is simple: a call comes in, agent qualifies and books, outcome gets logged to a sheet via n8n, and the owner gets a notification What's the part you're most stuck on right now?"