Master Retell AI with our step-by-step tutorial, detailed feature walkthrough, and expert tips.
Sign up for a free Retell AI account at dashboard.retellai.com — no credit card required for initial development. Create your first voice agent using a pre
built template (customer support or appointment booking) in the dashboard. Configure your LLM backend (GPT
1 recommended for cost/quality balance), system prompt, and voice from 6 TTS providers. Set up webhook endpoints for function calling if your agent needs to interact with external systems like calendars or CRMs. Test via the web
based calling interface (WebRTC), then connect a phone number via Twilio import or SIP trunking for production.
💡 Quick Start: Follow these 4 steps in order to get up and running with Retell AI quickly.
Explore the key features that make Retell AI powerful for voice agents workflows.
Proprietary orchestration layer that coordinates STT, LLM, and TTS with sub-800ms round-trip times by pre-processing audio for faster endpoint detection and streaming partial LLM outputs to TTS.
Building phone agents for appointment booking that respond naturally without awkward pauses, matching human conversation rhythm.
Advanced conversation management that detects and responds to user interruptions, backchanneling cues, and natural pause patterns rather than relying on simple silence detection.
Creating customer support agents that stop talking when interrupted and don't awkwardly talk over callers during natural conversation.
Mix-and-match architecture supporting 6 TTS providers (Retell Platform, ElevenLabs, Cartesia, Minimax, Fish, OpenAI) and 15+ LLM options across GPT-5 series, GPT-4.1, Claude 4.x, and Gemini with transparent per-minute pricing.
Pairing GPT-4.1 nano ($0.004/min) with Retell Platform voices ($0.015/min) for budget FAQ agents vs. GPT-5.2 with ElevenLabs for premium customer interactions.
Custom functions defined in agent configuration that trigger via webhook during live conversations, enabling real-time database queries, appointment scheduling, CRM updates, and call transfers.
An agent that checks appointment availability in your scheduling system, books the slot, and confirms with the caller — all within the same phone call.
Native support for Twilio number import, direct SIP trunking (no per-minute telephony charge), and WebRTC for web-based calling. Includes batch calling ($0.005/dial) and branded caller ID ($0.10/call) for outbound campaigns.
Migrating existing call center numbers from Twilio to Retell AI agents without changing phone numbers or customer-facing infrastructure.
Post-call analytics with sentiment analysis, topic detection, transcript generation, and conversation flow visualization. A/B testing compares agent configurations on live traffic. AI Quality Assurance available at $0.10/min.
Testing whether a friendlier system prompt increases appointment booking rates by running two agent versions simultaneously and comparing conversion metrics.
Retell AI uses modular per-minute pricing with three mandatory components: voice infrastructure ($0.055/min), TTS ($0.015-$0.040/min depending on provider), and LLM ($0.003-$0.16/min depending on model). Add optional extras like knowledge base (+$0.005/min), denoising (+$0.005/min), or PII removal (+$0.01/min). SIP trunking telephony is free; phone calls add ~$0.015/min. Realistic total: $0.10-$0.25/min for most production setups.
No, Retell AI is cloud-hosted only. The real-time voice orchestration runs on Retell's infrastructure. For HIPAA compliance, the Enterprise plan offers BAA agreements and data controls. For self-hosted alternatives, LiveKit provides open-source real-time audio infrastructure, though replicating Retell's turn-taking requires significant engineering.
For most use cases, GPT-4.1 ($0.045/min) or GPT-4.1 Mini ($0.016/min) paired with Retell Platform Voices ($0.015/min) offers the best balance. This gives you total costs of $0.115-$0.13/min with strong conversation quality. For budget agents handling simple tasks, GPT-5 nano ($0.003/min) brings total costs to ~$0.073/min.
Pay-as-you-go includes 20 concurrent calls, with additional capacity at $8/month per concurrent slot. Enterprise plans have no cap on concurrent calls and include dedicated server infrastructure for consistent performance under load.
Yes, Retell AI offers chat agents with per-message pricing separate from voice. Chat pricing ranges from $0.001/message (GPT-5 nano) to $0.03/message (Claude 4.5 Sonnet). Chat agents support SMS at $0.01/message and can share the same knowledge base and function calling setup as voice agents.
Now that you know how to use Retell AI, it's time to put this knowledge into practice.
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Tutorial updated March 2026