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Side-by-side facts to help you choose between voice agents or platforms.

Developer API

Vapi

Developer-oriented voice agent platform for building phone agents with custom workflows and integrations.

Voice Agent Platform

Voice AI platform for building low-latency phone agents across support, scheduling, and sales workflows.

Attribute	Vapi	Retell AI
Platform type	Developer API	Voice Agent Platform
Use cases	Customer Support Appointment Scheduling Lead Qualification Outbound Calling	Customer Support Appointment Scheduling Lead Qualification AI Receptionists
Useful for	• Developer teams • Custom call workflows • Voice AI prototypes	• Fast voice prototypes • Support call automation • Scheduling workflows
Integrations	Twilio Zapier Custom API CRM Calendar	Twilio Custom API Zapier CRM Calendar
Calls	Inbound, Outbound	Inbound, Outbound
Human handoff	Yes	Yes
Pricing model	Usage Based	Usage Based
Setup difficulty	Technical	Medium