Retell AI
Developer-first voice AI platform with low-latency LLM-powered phone agents
About Retell AI
Retell AI is an LLM-powered voice automation platform for building, deploying, and scaling AI voice agents that handle inbound and outbound phone calls. With ~600ms latency, a drag-and-drop agent builder, and BYO-LLM flexibility (GPT, Claude, Gemini), Retell powers receptionists, lead qualification bots, and large-scale outbound campaigns across healthcare, fintech, insurance, and logistics.
Pros & Cons
Pros
- Industry-leading ~600ms latency makes conversations feel genuinely natural
- BYO-LLM flexibility lets you tune cost vs quality per agent (GPT-4o, Claude, Gemini)
- Pure pay-as-you-go pricing with no monthly minimum — start at $0
- Strong developer tooling: APIs, webhooks, SIP trunking, and SDKs
- Enterprise-grade compliance baseline (HIPAA, SOC 2, GDPR) even on lower tiers
Cons
- Per-minute costs stack quickly when adding LLM, TTS, knowledge base, and PII redaction
- Voice-first focus — limited native SMS/email/webchat orchestration compared to omnichannel platforms
- Configuration is more technical than no-code competitors; non-developers may struggle
- Pricing complexity makes forecasting difficult at scale (multiple a la carte add-ons)
Key Features
Low-Latency Voice (~600ms)
Sub-second response time enables natural, fluent back-and-forth conversations
BYO-LLM Architecture
Choose GPT, Claude, or Gemini models per agent — pay infrastructure cost separately from LLM cost
Drag-and-Drop Agent Builder
Visual agentic framework with built-in guardrails and prompt templates
Real-Time Function Calling
Agents book appointments, process payments, transfer calls, and trigger webhooks during live conversations
Knowledge Base + Streaming RAG
Automatic syncing keeps agents grounded in up-to-date documents and FAQs
Batch Calling
Run unlimited concurrent outbound campaigns without provisioning constraints (Enterprise)
Post-Call Analytics
Performance dashboards, transcripts, sentiment, and call success metrics
Enterprise Compliance
HIPAA, SOC 2 Type II, GDPR, PII redaction, SSO, and custom roles
Pricing
- $10 free credits to start
- 20 concurrent calls included
- Voice: $0.07-$0.31/min (LLM dependent)
- Chat: $0.002+ per message
- Full platform access, no contracts
- Pre-built templates and webhooks
- Dedicated stable server
- Unlimited concurrent calls
- Custom MSA/DPA/BAA
- On-premises deployment option
- SSO and custom RBAC
- Priority support and SLA
Best For
AI Receptionist
24/7 phone answering with appointment booking and call transfers for clinics, agencies, and SMBs
Outbound Lead Qualification
Batch-call leads, qualify intent, and hand off to human reps via warm transfer
Healthcare Patient Outreach
HIPAA-compliant reminders, intake, and follow-up calls with PII redaction
Customer Support Automation
Tier-1 voice support with knowledge base RAG and escalation paths
Logistics Dispatch
Automated driver check-ins, ETA confirmations, and exception handling
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