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Build a Voice AI Agent That Handles Inbound Calls End to End

Answer real phone calls with an AI agent that transcribes, reasons, and responds in natural speech, and knows when to hand off to a human.

Time Required

1-2 days, one-time setup

Expected Result

A working voice agent that answers real inbound calls, understands callers through real-time transcription, responds with natural speech, and escalates to a human at defined limits instead of improvising past them.

Recommended Tools

1

Pick Vapi or Retell AI Based on Your Telephony Stack

Both platforms handle the full voice pipeline (speech-to-text, LLM reasoning, text-to-speech) end to end. The real decision factor is which one integrates more cleanly with your existing phone number provider and CRM, not a feature difference between them.

Vapi
Retell AI
2

Wire Up Real-Time Transcription with Deepgram

Connect Deepgram's speech-to-text API for the inbound audio stream so the agent has an accurate, low-latency transcript of what the caller is actually saying to reason over.

Deepgram
3

Write the Agent's Call-Handling and Escalation Rules

Define what the agent should try to resolve on its own (order status, appointment scheduling, FAQ-style questions) versus a fixed list of triggers that hand off to a human immediately (anger detected, an explicit request for a person, anything touching payment or legal). An agent that doesn't know its own limits is the real customer-experience risk here.

4

Generate the Agent's Voice with ElevenLabs

Connect ElevenLabs for the text-to-speech side so responses sound natural rather than robotic, which matters more on a phone call than in a chat window since tone is the entire signal.

ElevenLabs
5

Test on Real Call Scenarios Before Going Live

Run the agent through transcripts of your actual common requests, plus a few deliberately confusing or hostile ones, and confirm it escalates correctly rather than confidently mishandling a call it should have handed off.

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