Vapi

The developer platform for voice agents: assemble sub-second phone-call AI from best-in-class STT, LLMs and TTS — with phone numbers, transfers, and integrations — without building the telephony plumbing yourself.

Product preview

Overview

Vapi bundles the entire misery of production voice AI — telephony, jitter buffering, interruption handling, endpointing, provider failover — behind one API, so developers assemble agents from the best components (Deepgram or AssemblyAI for ears, GPT/Claude for brains, Cartesia or ElevenLabs for voice) and get a phone number that answers in under a second.

It is infrastructure with an opinion but not a cage: every layer is swappable, costs pass through at provider rates plus platform margin, and observability shows each turn of every call. Compared with building on Twilio raw (months of audio engineering) or vertical products (no flexibility), Vapi is the middle path that made phone AI a feature any startup can ship. Pricing is usage-based; quality depends on the components you choose.

Pros / Cons

Pros

Skips months of telephony audio engineering
Every component swappable — no lock-in to one model
Call-level observability and testing built in
Multilingual and transfer flows included

Cons

Usage costs stack across three providers plus platform
Latency depends on your chosen components
Young platform — APIs still evolving

Who it's for

AI receptionists and outbound sales callers

Automated restaurant/clinic bookings

Customer support overflow lines

Voice surveys and reminder systems

Bottom line

The Twilio of the voice-agent era — assemble a phone AI in a week instead of a year.

Key Features

Sub-second voice agent loop

BYO models (STT/LLM/TTS) or defaults

Phone numbers, transfers & IVR flows

Multilingual calling

Native CRM & calendar integrations

Compare Vapi with alternatives

Vapi vs Hugging Face Vapi vs Replicate Vapi vs Ollama 4 products · AI Platforms

Frequently asked questions

What is Vapi?

Vapi is a AI Platforms tool developed by Vapi. The company was founded in 2023 and is headquartered in San Francisco, USA. The developer platform for voice agents: assemble sub-second phone-call AI from best-in-class STT, LLMs and TTS — with phone numbers, transfers, and integrations — without building the telephony plumbing yourself.