Vapi is the infrastructure layer for AI that talks on the phone: a developer platform that orchestrates speech recognition, LLMs, and voice synthesis into low-latency voice agents that can handle real calls at scale.

Building a voice agent means juggling telephony, streaming transcription, turn-taking, interruption handling, LLM latency, and natural-sounding TTS, all within the sub-second budget human conversation demands. Vapi packages that pipeline behind clean APIs and SDKs: pick your STT, LLM, and voice provider (or bring your own keys), define the agent's behavior and tools, and deploy to phone numbers, web, or mobile. Function calling lets agents book appointments, look up orders, and transfer to humans mid-call; workflows, squads of agents, testing suites, and call analytics cover the production lifecycle.

Its provider-agnostic design is the differentiator: swap models and voices as the market improves without rebuilding your stack.

Who is it for?

Developers and startups building phone agents for support, scheduling, intake, and outbound, and enterprises replacing legacy IVRs with something customers do not hate.

How much does Vapi cost?

Usage-based: a small platform fee per minute (around $0.05) plus pass-through costs of your chosen providers, with free credits to prototype and volume/enterprise pricing at scale.

Our verdict

Vapi has become the default answer to "how do we ship a voice agent without building a lab". You still design the conversation, but the hard real-time engineering is solved, and the provider flexibility future-proofs the investment.