Retell AI
Voice-AI platform for building inbound and outbound phone agents. Provides telephony, voice synthesis, multiple agent types (single-prompt / multi-prompt / conversation-flow), function calling for tool use, and webhook delivery of post-call data. The voice front-end of the no-code receptionist pattern documented in summary-zubair-trabzada-retell-voice-agent.
Agent types
- Single-prompt — easiest, flexible enough for receptionist-style work
- Multi-prompt — multiple personas/structures for branching conversations
- Conversation flow — rigid, for highly formatted scripted calls
Built-in functions
check_calendar_availability/book_appointment(cal.com integration via event_type_id)transfer_call(cold or warm transfer with target number)end_call- Custom HTTP-based functions for arbitrary tool calls
Cost reference
GPT-4.1 Mini “Fast” voice ≈ $0.094/min at the time of summary-zubair-trabzada-retell-voice-agent.
Pairs with
- n8n — for post-call CRM updates via webhook + structured output parser
Sources
See Also
- ai-automation-workflows — broader playbook