What is the best voice agent API for developers?

It depends on what you bring. If you have a SIP trunk and want one prepaid balance across engines, Wixzel Phone. If you need SDKs, provisioned numbers, web calling and a mature platform, Vapi or Retell AI. If you want a single-vendor integrated stack with enterprise terms, Bland AI. If you want to self-host and own the pipeline, Pipecat or LiveKit Agents.

Which voice agent API is cheapest?

Only comparable once telephony and provider costs are included, and those depend on your carrier and your choice of models. Wixzel Phone publishes generated prices from $0.0466 to $0.1851 per connected minute with telephony at your carrier's rate and no provider bills. The other platforms publish a platform fee with provider and telephony costs on top; check their pricing pages, which change by tier.

Do I need my own SIP trunk for these?

For Wixzel Phone, yes; it does not sell numbers. Vapi, Retell AI and Bland AI will provision a number for you and also accept a trunk. Pipecat and LiveKit Agents need you to integrate telephony yourself or through a provider.

Which voice agent API is best for Indian languages?

Wixzel Phone's sarvam engine runs Sarvam's Saaras, Sarvam-105B and Bulbul models end to end for Hindi, Tamil, Telugu and other Indian languages. Other platforms can reach Indian-language models where they expose them as providers; check each catalogue.

How was this list put together?

By the operator of Wixzel Phone, so read the house entry as the interested party it is. Each other product is described from its own public documentation as of 2026-09-08, at the level of business model rather than rate, and each is named as best for something real. Corrections are welcome at the address on the contact page.

Roundup

Best voice agent APIs for developers in 2026

Who picks what, in three lines: developers with a SIP trunk who want one prepaid balance pick Wixzel Phone; teams that want SDKs, provisioned numbers and a mature platform pick Vapi, Retell AI or Bland AI; teams that want to own the pipeline pick Pipecat or LiveKit Agents.

Last updated 8 September 2026

Written by the operator of Wixzel Phone. The house entry gets the most depth and its limitations are listed; every other entry is described from its own public documentation and named as best for something real.

At a glance

Product	Best for
Wixzel Phone	developers who bring their own SIP trunk and want one prepaid balance to cover every engine
Vapi	teams that want a mature, feature-rich platform with SDKs, provisioned phone numbers, web calling and the option to bring their own provider keys.
Retell AI	teams that want a conversation-flow builder, provisioned numbers, batch campaigns and analytics in one product, with an API underneath.
Bland AI	teams that want an integrated voice stack from one vendor, conversational pathways for designing calls, and enterprise options such as dedicated infrastructure.
Pipecat	teams that want to self-host an open-source voice pipeline and wire providers themselves
LiveKit Agents	teams already on LiveKit or WebRTC who want an open-source agent framework with a hosted option

1. Wixzel Phone

Best for developers who bring their own SIP trunk and want one prepaid balance to cover every engine

Wixzel Phone is an API for building AI voice agents that place and answer real phone calls over your own SIP trunk. One API key and one prepaid balance cover every voice engine, billed per second of actual usage. Engines are presets (classic, sarvam, gemini-live, deepgram-agent) or composed stage by stage from named provider/model pairs, and the sarvam engine covers Indian languages end to end. Every price on the site is generated from the price book the meter bills against, and every charge is itemised per usage row.

Pricing. $0.0466 (gemini-live) to $0.1851 (deepgram-agent) per connected minute at typical speech rates, including a $0.012 per minute orchestration fee. Prepaid, $5 minimum top-up, no subscription. Telephony is your own trunk and is not marked up.

Limitations, honestly

Alpha. Behavioural changes ship behind a dated Wixzel-Version header, but the product is months old and operated by one person.
No SDK. The API is plain HTTP and JSON with an OpenAPI document.
No phone numbers or minutes sold. A SIP trunk is required before the first call.
No browser or web calls; telephony only.
No visual agent builder. Agents are created through the API.
Fewer providers than the platforms below: Deepgram, ElevenLabs, OpenRouter, Sarvam and Google today.

All Wixzel Phone facts

2. Vapi

Best for teams that want a mature, feature-rich platform with SDKs, provisioned phone numbers, web calling and the option to bring their own provider keys.

Vapi is a developer platform for building voice AI agents, with SDKs, a web dashboard, phone number provisioning and a large catalogue of pluggable speech and model providers.

Wixzel Phone vs Vapi

3. Retell AI

Best for teams that want a conversation-flow builder, provisioned numbers, batch campaigns and analytics in one product, with an API underneath.

Retell AI is a platform for building and deploying AI phone agents, with a conversation-flow builder, phone number provisioning, SIP support, batch calling and analytics.

Wixzel Phone vs Retell AI

4. Bland AI

Best for teams that want an integrated voice stack from one vendor, conversational pathways for designing calls, and enterprise options such as dedicated infrastructure.

Bland AI is a platform for AI phone calls that runs its own end-to-end voice stack, with conversational pathways, phone number provisioning, batch calling and enterprise deployment options.

Wixzel Phone vs Bland AI

5. Pipecat

Best for teams that want to self-host an open-source voice pipeline and wire providers themselves

Pipecat is an open-source Python framework for building realtime voice and multimodal agents. You run it, choose and pay each provider directly, and own the orchestration code. The trade is control and zero platform fee against operating the pipeline, the telephony integration and the provider accounts yourself.

Pipecat on GitHub

6. LiveKit Agents

Best for teams already on LiveKit or WebRTC who want an open-source agent framework with a hosted option

LiveKit Agents is an open-source framework for realtime voice agents on top of LiveKit's WebRTC infrastructure, with SIP support and a cloud offering. It suits products that also need browser or app calling, or that already run LiveKit rooms. You bring provider keys and, unless you use the cloud, run the infrastructure.

LiveKit Agents on GitHub

How this list was put together

Products were included if a developer could build a phone-calling AI agent on them today, and each was described from its own public documentation at the level of business model: who owns the provider accounts, who sells the telephony, how it is billed, and how mature it is. Rates were left out because they change by tier and by month. Carriers and model vendors were left out because they are parts of these stacks, not alternatives to them. Corrections are welcome via the contact page.

Frequently asked questions

What is the best voice agent API for developers?: It depends on what you bring. If you have a SIP trunk and want one prepaid balance across engines, Wixzel Phone. If you need SDKs, provisioned numbers, web calling and a mature platform, Vapi or Retell AI. If you want a single-vendor integrated stack with enterprise terms, Bland AI. If you want to self-host and own the pipeline, Pipecat or LiveKit Agents.
Which voice agent API is cheapest?: Only comparable once telephony and provider costs are included, and those depend on your carrier and your choice of models. Wixzel Phone publishes generated prices from $0.0466 to $0.1851 per connected minute with telephony at your carrier's rate and no provider bills. The other platforms publish a platform fee with provider and telephony costs on top; check their pricing pages, which change by tier.
Do I need my own SIP trunk for these?: For Wixzel Phone, yes; it does not sell numbers. Vapi, Retell AI and Bland AI will provision a number for you and also accept a trunk. Pipecat and LiveKit Agents need you to integrate telephony yourself or through a provider.
Which voice agent API is best for Indian languages?: Wixzel Phone's sarvam engine runs Sarvam's Saaras, Sarvam-105B and Bulbul models end to end for Hindi, Tamil, Telugu and other Indian languages. Other platforms can reach Indian-language models where they expose them as providers; check each catalogue.
How was this list put together?: By the operator of Wixzel Phone, so read the house entry as the interested party it is. Each other product is described from its own public documentation as of 2026-09-08, at the level of business model rather than rate, and each is named as best for something real. Corrections are welcome at the address on the contact page.