What this is: the universal blueprint for a phone agent that answers every call, books appointments and never puts anyone on hold. One architecture, any industry — salon, clinic, restaurant, auto service, real estate. Stack: Retell AI (the voice) + Claude (the brain). First ~60–90 minutes of calls are free.

Thanks for commenting VOICE! This is the full playbook from the reel.

The architecture (5 blocks — same for every business)

Call → Voice → Brain → Flow → Booking

1. The Call — agent picks up on the first ring, 24/7. A missed call is usually a lost booking; this removes the concept.
2. The Voice — cast it like an actor: calm for a clinic, warm for a salon, brisk for a restaurant. Slow the speaking rate slightly — confident agents don't rush.
3. The Brain — Claude + a system prompt that works like a job description: what it books, what it never promises, when it hands off to a human.
4. The Flow — one question at a time, then one clear confirmation sentence. Confirmation discipline separates an agent from a toy.
5. The Booking — calendar event + log row + a ping to the owner only when a human is needed.

Setup in 6 steps (Retell AI)

1. Account: retellai.com → sign up → $10 free credits (≈60–90 min of calls, no card needed). Production later: ≈$0.11–0.15/min all-in.
2. Create agent: Agents → Create → single-prompt agent. LLM: pick a Claude model (fast tier is enough and keeps per-minute cost low). Temperature ≈0.7.
3. Voice: audition 3–5 from the library per the casting notes above. This choice does more for perceived quality than any prompt tweak.
4. System prompt: paste the universal template below, fill the brackets.
5. Test: web-call it from the dashboard 5–10 times. Try being confused, rushed, angry — fix what breaks by adding one rule per problem.
6. Phone number (production): attach a number inside Retell (or via Twilio) when you're ready for real callers.

The universal system prompt