Top 10 AI Voice Agent API and SDK Providers [2025]

Want to build a voice assistant like Alexa or Siri for your business?

If you’re building an AI-powered voice app or service, go with an AI Voice Agent API or an SDK to create smart, helpful voice features in your app within hours.

Confused about which API/SDK to choose? In this article, we will review Top 10 AI Voice Agent API and SDK Providers. Carefully compare their features, pricing, and ease of use to find the right fit for your project.

What Is An AI Voice Agent?

An AI voice agent is a smart virtual assistant that can listen to what people say, understand the meaning, and respond naturally, just like how a human would. 

It’s used to handle everyday operations like customer support, answering questions, or helping with tasks like booking appointments or processing orders.

To do this, it uses a mix of technologies:

• ASR (Automatic Speech Recognition) to turn the words we speak into text
• NLU (Natural Language Understanding) to figure out what exactly the person means
• Dialogue Management to decide how to respond
• TTS (Text-to-Speech) to talk back to the user

These voice agents can work over phone calls, inside mobile apps, or on voice-enabled devices like smart speakers.

How to Choose the Right AI Voice Agent API and SDK Provider

If you’ve decided to build your AI voice agent with a pre-built API or SDK, here are a few things to keep in mind:

• Is the API/ SDK easy to integrate?

Going with a ready-made solution will make your development process easier. But what if the API you choose complicates it? 

Not all, but a few APIs in the market might make the AI agent implementation daunting without a low-code approach and messy documentation. A good API documentation usually gives you the first impression of how well the APIs will work for your platform. Take a glance at them first. 

• What languages and models does it offer?

Purchasing an API is a long-term investment. Make sure that the provider you choose supports the technology you need for your AI agent. If they do not, it is better to go for a platform that offers all the modern technology. 

• Does it include testing and monitoring tools? 

You can purchase an AI agent solution with one provider and buy a testing tool from another provider. That drains your money, time and energy. 

Instead look for a provider that includes built-in testing features and performance dashboards.

• How scalable is the solution?

Implementing a voice agent with AI capabilities could lead to more inquiries. Sometimes, the number of calls might go off the roof, as your business flourishes. 

The solution you pick must be able to handle this shift in the number of calls your platform will receive without degrading the performance or quality of calls. 

• Does it come with built-in security and storage?

Look for a solution that has end-to-end encryption features along with adherence to industry standards like GDPR, and HIPAA. 

Do not choose solutions that compromise on the security and privacy features, which would put your brand reputation at a serious stake. 

• What is the pricing model?

APIs are available at different pricing models – pay per minute, per call or a flat monthly fee. See which of these models fit your budget and usage and choose it. 

Top 10 AI Voice Agent API and SDK Providers

The Top 10 AI Voice Agent APIs & SDKs in 2025 are Apphitect, MirrorFly, Vapi AI, Twilio, Retell AI, Cognigy, Sendbird, Yellow AI, Voiceflow and Speechly.

1. MirrorFly

Best for: Enterprises that need fully customizable, white‑labeled, voice chat with complete data control.

MirrorFly is a leading CPaaS (Communication Platform as a Service) provider that offers a fully customizable AI Voice agent solution for both web and mobile apps.

The platform leads the list with its 100% customization options along with full data ownership. This means, you have all the control over how you’ll build your AI voice agent. 

Trusted by over 500 brands, MirrorFly comes with built-in encryption features to secure every conversation between your customers and your AI Voice Agent. 

The key highlight of MirrorFly’s security features is – they are completely customizable. You can add any number of encryption layers and privacy features to protect your user data. Additionally, you can also build your voicebot with region-specific compliances. 

Here’s why businesses are choosing MirrorFly for their AI Voice solutions:

MirrorFly’s fully customizable AI-powered Voice Call API & SDK provides fully secure SIP/VoIP calling with end-to-end encryption. You can easily integrate a smart voicebot into both web and mobile apps, within 48 hrs. 

What are the Key Features of MirrorFly?

• 1:1 Voice Calling
• Unlimited Group Voice Calling
• High-Definition SIP & VoIP Audio 
• Live Audio Broadcasting 
• Message History & Backup
• Real-time in-call controls 
• Presence Indicators
• File and Media Sharing
• Typing Indicators
• Read Receipts and Delivery Status
• Push Notifications
• Profanity Filters
• Chat Moderation Tools
• Chat Export

Use Cases:

• Contact center operations 
• Helpdesk support
• Multi-Party Calling for team discussions 
• Audio Streaming Events for large audience engagement
• Video KYC for Fintech
• Visitor authentication for Gated Communities

On the whole, MirrorFly’s Voice Agent solution is a perfect combination of custom security, white‑labeling options, feature-richness and conference scalability. 

2. Sendbird

If you are looking for a Voice AI agent solution that is reliable and developer-friendly, Sendbird might work for you well. 

Sendbird is known for its seamless integration and in-app performance, while offering perfect quality. 

Businesses using Sendbird’s messaging stack already will find its Voice AI Agent quick and instant for implementation.

Why Sendbird AI Voice Agent Solution: Sendbird’s Call SDK enables cross-platform voice and video calls across Android, iOS, JavaScript, Unity, and React Native. It also includes a Platform API that gives you full control over call management and customization from the server side.

What are the Key Features of Sendbird?

• Real-Time Voice chat & Video with smart network adaptation for stable performance
• Server-Side API for voice call moderation and custom metadata handling
• Call Recording, Transcription, and Media Streaming support
• End-to-End Encryption options for secure, private communication

• Smart network adaptation for better call quality
• Call recording and transcription
• End-to-end encryption for secure conversations
• Event handlers to manage call rooms and user interactions

Use Cases:

• Telehealth Consultations directly within mobile apps for real-time doctor-patient interaction
• In-Game Voice Chat for smooth communication during multiplayer gameplay
• Social Networking Apps with Live Voice Rooms for interactive, audio-based engagement

In a nutshell, Sendbird is ideal for developers looking to perform AI Voice Agent Integration with seamless multimedia chat, including voice, video, and messaging, alongside robust backend control for managing calls, users, and metadata with precision.

3. Apphitect

Best for: Organizations that require self‑hosted, customizable chat with voice and video modules.

Most popular brands go for Apphitect’s Voice AI Agent for its customizable solution that gives full control of user data in your hands. It is indeed a best option for teams needing strict compliance and flexible deployment control. 

You can host your AI agent on your own servers or on Apphitect’s cloud servers depending on your requirements. 

If you are prioritizing data security along with customization, Apphitect is a must-try!

Why Apphitect Voice Agent Solution?

Apphitect provides a fully hostable messaging stack, allowing you to own all your data and seamlessly integrate voice and instant messaging APIs directly into your own infrastructure for complete control and customization.

What are the Key Features of Apphitect?

• Self-Hosted Chat API & SDK 
• Voice, Video, and Rich-Media Messaging 
• Telecom-Grade Reliability 
• Modular Design

Use Cases:

• Telecom Network Maintenance Coordination for seamless communication during updates
• Internal Corporate Communication Systems for efficient team collaboration
• Secure Messaging for government or healthcare applications, ensuring confidentiality and compliance 

In brief, Apphitect works best in situations where it’s important to keep full control of your data and customize everything to fit exactly what you need. You get to manage your own setup and tweak things however you want.

4. Twilio

Best for: Developers who need programmable inbound/outbound voice and IVR at scale.

Twilio’s Voice Agent Solution is a safe, future-ready choice for teams that need reliable in-app voice call SDKs and APIs for building AI-powered Voice Agents. 

Businesses that invest on Twilio usually count on a high availability, and unmatched scalability. Their years of experience help them keep innovating their features, keeping your voicebots modern with evolving demands.

Why Twilio Voice Agent Solution?

Twilio Programmable Voice delivers global telephony, SIP trunking, and programmable media streams for interactive voice experiences.

What are the Key Features of Twilio?

• Inbound/outbound call API with call control
• Conference calls and warm transfers
• IVR, speech recognition, and recording
• Real‑time Media Streams via WebSockets

Use Cases:

• Call‑center automation and customer surveys
• Appointment reminders and two‑factor authentication
• Real‑time voice analytics for compliance

To sum up, Twilio is a popular choice for voice features because it has a well-developed platform and can connect calls almost anywhere in the world. It’s great for building flexible voice systems.

5. Vapi AI

Best for: Rapid development of multilingual AI voice agents with deep configurability.

If you want more than just a plug-and-play tool to manage customer interactions with voicebots, Vapi AI would be a great choice. 

It is an agile platform that helps you build advanced voice agents that you can experiment, iterate and fine-tune over time.

Why Vapi AI Voice Solution?

Vapi is built to work directly through APIs, supports over 100 languages, lets you run automated tests, and even allows you to use your own AI models, making it a solid choice for large-scale business setups.

What are the Key Features of Vapi?

• Multilingual ASR/NLU in 100+ languages
• Fully API‑native with thousands of config options
• Automated test suites for hallucination risk analysis
• Custom model integration via API endpoints
• Customizable voice assistant API

Use Cases:

• Global customer support automation
• Voice technology-driven surveys and analytics
• Scalable call‑center assistants

To summarize, Vapi is great for situations where you need to support many languages and make sure everything can be easily tested.

6. Retell AI

Best for: Teams seeking an intuitive builder plus testing and monitoring capabilities.

Retell AI is a good choice for businesses that compromise neither on flexibility nor on speed. 

Its design is perfect for developers. It supports quick iterations along with real-time insights to make improvements. 

Developers can get actual performance data to understand the voice strategies they need for fine-tuning the AI voice agent for business operations. 

Why Retell AI Voice Agent Solution?

Retell AI combines a developer‑friendly REST API with a low‑code agent builder and builtin test harnesses to ensure robust dialogue flows.

What are the Key Features of Retell?

• Visual agent builder for rapid prototyping
• REST API for custom integrations.
• Deployment to phone calls, web calls, and SMS
• Dashboard for monitoring success rates and sentiment 

Use Cases:

• Automated appointment scheduling via voice or SMS
• Interactive voice surveys with sentiment tracking
• Hybrid voice‑chat customer support
  

In essence, Retell AI makes implementing voice agents easier while giving developers enough control to customize how it works.

7. Cognigy

Best for: Large‑scale IVR systems requiring complex dial logic and CLI tooling.

Cognigy is an AI voice agent platform that gives full control over every part of the voice workflow. 

If you are looking for structured AI-powered  voice automation along with cross-team collaboration, this platform will align with your strategy. 

Speaking of its scalability, you can easily plug the agent into large-scale environments easily with this solution.

Why Cognigy AI Voice Agent Solution?

Cognigy’s voice system can handle touch-tone input (like pressing buttons on your phone), deals well with errors, and comes with tools developers can use to automate and manage updates easily.

What are the Key Features of Cognigy?

• Dial‑logic driven conversation flows.
• API and CLI toolsets for automation.
• Enterprise security and compliance features
• Integration with CRM and backend systems

Use Cases:

• Complex IVR for banking and insurance
• Self‑service customer portals
• Automated outbound call campaigns
• To put it simply, Cognigy is designed for big companies that rely heavily on phone systems and can’t afford downtime.

8. Yellow AI

Best for: Omnichannel bots that need external API orchestration.

Businesses sometimes need to handle complex workflows. Yellow AI helps them build voice agents for them quickly and easily, with secure integrations. This solution is indeed a sound investment for businesses looking to benefit from a global infrastructure without compromising on agility.

Why Yellow AI Voice Agent Solution? 

Yellow.ai offers an API  that lets you manage complex operations like user information, events, notifications, and integrations with other services in your voice or chat agents, effortlessly

What are the Key Features of Yellow AI?

• Add/import custom APIs for dynamic data retrieval
• Outbound notifications and email ticketing
• User‑event tracking and analytics
• Low‑code studio for rapid agent composition

Use Cases:

• E‑commerce order status bots
• Real‑time logistics tracking via voice
• Support ticket creation and escalation

Altogether, Yellow.ai is perfect for businesses looking to smoothly manage and connect interactions across multiple communication channels.

9. Voiceflow

Best for: Designers and developers prototyping and launching voice experiences quickly.

Running a cross-functional team? Voiceflow is a strong fit for your business. You can take full control of your voice agent’s performance and logic, prototype it, manage and evolve, with full oversight. 

This means, the iteration cycles will come down with a clean transparency of how your voice agent is performing.
Why Voiceflow AI Voice Agent Solution? 

Voiceflow’s API suite allows you to automatically create, host, and manage chat or voice agents, while also providing tools for designing their interactions visually.

What are the Key Features of Voiceflow AI?

• APIs to start and stop agent sessions
• Versioning and environment management
• Webhooks for event‑driven workflows
• SDKs for JavaScript and TypeScript development.

Use Cases:

• Educational chatbots for e‑learning
• Marketing voice campaigns in Alexa or Google Assistant
• Internal knowledge‑base assistants
   

Taking everything into account, Voiceflow is great at connecting design and coding, making it easy to create voice agents that work across multiple platforms.

10. Speechly

Best for: Developers needing first‑class ASR/NLU with client‑side audio handling.

Speechly is a top pick for businesses that want to build responsive voice-enabled interfaces, without relying too much on the cloud infrastructure. 

You get full freedom to deploy the agent wherever you want – on-premise, or on edge servers just as your business demands.

Why Speechly AI Voice Agent Solution? 

Speechly offers fast speech-to-text conversion and intent recognition through a public API and easy-to-use client libraries for both web and mobile applications.

What are the Key Features of Speechly AI?

• Public API specs with generated client code
• Microphone and audio management functions
• State management for continuous dictation
• Support for multiple platforms via client voice SDKs 

Use Cases:

• Voice command interfaces in SaaS dashboards
• Real‑time transcription services
• Interactive voice workflows in mobile apps

Everything considered, Speechly is the ideal choice for quickly integrating voice-based user interfaces that focus on the needs of the client.

Developers Pick: MirrorFly And Apphitect

MirrorFly and Apphitect are two best communication solutions that are carefully built for businesses that need customizable, high-quality, secure, and flexible voice solutions. If you’re looking to build or manage AI-powered voice agents, these platforms are equipped to give you everything you need.

Here’s why you’ll find them among the top choices for AI Voice Agent SDKs and APIs.

1. 100% Customization

You’re in charge of how your AI voice agent will work. If you need to tweak a button or adjust the workflow, you can do it all yourself. There are no limitations. 

The voice APIs and SDKs are open to make changes so you can build your voice agent just exactly how your business needs.

2. 100% Data Control

Every information your users share (names, inquiry details, contact details, call recordings, chat logs) are stored on the server you choose – on-premise, in your own cloud account or on both, just as you choose it. 

You don’t have to worry about third-parties peeking into user conversations with your voicebots. These providers come with robust encryptions along with two-factor authentication, custom encryptions you can choose, and even rules that block certain countries from accessing the data.

3. Self-managed Deployment

Whether your business needs your user data to store it in your own servers, in your own country, or maybe you want to conveniently store it in a public cloud, MirrorFly and Apphitect’s self-hosted solutions allows you to go with your choice without any restrictions. 

4. SIP/ VoIP Solution

Both the platforms are pioneers in the CPaaS industry. They’ve built the solution to place and receive calls over the internet (VoIP) and manage them with SIP. With these SIP/ VoIP solutions overall, you’ll not require any complex hardware or software for the setup. It’s all already built. 

5. White-label your Voice Agent

If you want the Voice agent in your app or web chat to look like it’s yours from top to bottom, you can add your company logo, colors and even custom elements. Your customers see only your brand.

6. Profanity Filters

Don’t worry about swear words or any language you consider off-limits, that might degrade the integrity of your app. These platforms come with built-in profanity filters to block them all. You define the list, and the system automatically mutes or replaces those words so conversations stay professional. 

7. WebRTC

Your users can talk or video-chat directly in their browser. They’ll not need any additional downloads or installs. Your voice agents will work in real-time without the need for the customer to wait for a response, using WebRTC protocol. 

8. Unlimited Chats & Calls

Whether you have ten users or ten thousand, you need not worry whether your voice agent can handle them or not. The system is designed so you can handle as many simultaneous voice or chat sessions as you need.

9. Multi-language Support

You can create agents that understand and reply in your customers’ native languages – whether that’s English, Spanish, Hindi, or any. This helps you support a global audience without juggling multiple systems.

10. 100+ Third-party integrations

Need your voice agent to log tickets in Zendesk, update records in Salesforce, or trigger messages in Slack? Add any plugin or extension to expand the capabilities of your app, effortlessly.

Overall, MirrorFly and Apphitect are top choices for building AI voice agents. They’re customizable, secure, easy to scale, and can be hosted on any server. If you’d like to know more about these solutions, post your queries in the comment section below or contact their team by filling out this quick form.