Ahmad AffanAI voice agents
AI voice agents that answer the phone, book the job and hand off cleanly.
I build phone assistants that talk naturally, check real availability, create the booking while the caller is still on the line and pass hot calls to a person.
A voice agent chains speech recognition, a language model and speech synthesis over a phone line, usually within a second or two. The hard part is not the voice. It is giving the agent the right tools: live calendar availability, your pricing rules, your CRM, and a safe way to say “let me transfer you.”
I have built both sides: a booking SaaS where a phone agent talks to a custom model over WebSocket with function calling, and an outbound control panel where staff design assistants, upload leads and launch campaigns. I understand the platform layer and the product around it.
Appointment-booking receptionists
Answer after hours, check availability, book, reschedule and cancel, then send confirmations.
Lead qualification calls
Ask your screening questions, score the lead, and push the answers into your CRM or Telegram.
Outbound follow-up campaigns
Call a list of leads with an approved script, respect do-not-call lists and log every outcome.
Reminder and no-show calls
Confirm visits, fill cancelled slots and reduce missed appointments.
FAQ and order-status lines
Answer the same ten questions all day so your team can focus on real work.
Hot-transfer to a human
Detect urgency or intent and transfer the live call, passing a summary to the person who picks up.
Conversation design
System prompt, opening line, tone, tools and guardrails, tested against real call scenarios.
Voice platform setup
Agents on Retell or Vapi, phone numbers, voices, models and call settings.
Custom LLM and tools
A WebSocket backend with function calling so the agent can read your data and act on it.
Booking and calendar logic
Real availability checks, time-zone handling and booking rules that match how you work.
CRM, webhooks and alerts
Call results sent to your systems, with Telegram or email alerts for hot leads.
Dashboards and call logs
A control panel for transcripts, outcomes, assistants and campaigns.
Testing and monitoring
Scenario scripts, cost per minute tracking and alerts when calls go wrong.
| Voice platforms | Retell AIVapi |
|---|---|
| Language model | OpenAI function callingCustom LLM WebSocket |
| Backend | FastAPIDjango REST FrameworkCelery |
| Data | MongoDBPostgreSQLRedis |
| Integrations | Google CalendarStripeTelegram Bot APISMTP email |
| Front end | ReactTypeScript |
Pick one call to automate
Start with the most repetitive, highest-value call type, not the whole phone line.
Write the playbook
What the agent may say, what it must check, when it transfers, and what it must never promise.
Build the tools
Calendar, CRM and webhook integrations the agent calls during the conversation.
Test with real scenarios
Messy callers, accents, interruptions, wrong numbers and edge-case requests.
Launch and tune
Go live on a small share of calls, review transcripts, adjust prompts and expand.
Latency is a feature
One independent real-phone-call benchmark measured median replies of about 1.6 s on Vapi and 1.7 s on Retell. Another measured about a second. Results depend heavily on setup, so I measure your agent from the caller’s side.
Cost per minute adds up
As of October 2026 Vapi lists $0.05/min hosting and Retell from $0.07/min, but the model, voice and phone line are billed on top. All-in costs commonly land around $0.10–$0.30 a minute, so I model your volume first.
Always allow a human exit
A clear transfer path protects customers and your reputation.
Recording and outbound-calling rules
Consent, recording and calling-hours rules differ by country and state. Get proper advice for your market.
It turns the caller’s speech to text, sends it to a language model that decides what to say or which tool to call, then turns the reply back into speech, all within about a second or two.
Retell is quicker to configure for booking flows. Vapi gives a developer more control over each component. I pick based on how custom your logic needs to be.
Yes. It checks live availability and creates the appointment while the call is still going, then confirms by message.
Per-minute platform and model costs plus a phone number. I give you an estimate from your expected call volume.
It is built to say so and offer to transfer or take a message, instead of guessing.
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