👁️🗨️ Voice Intelligence
The leading voice agent APIs offer lifelike speech synthesis, robust conversational logic, and scalable telephony integration. Choose based on your specific needs:
Top Recommendations
1. Lindy
What does it do? Lindy is a no-code voice agent platform that can take calls, hold real conversations, qualify leads, send follow-ups, and update your systems without human input.
Who is it for? Perfect for teams that deal with sales calls, support tickets, recruiting, or client onboarding.
Lindy can make and take real phone calls. And yes, it ACTUALLY sounds like a person. Built with drag-and-drop flows, no coding required.
Key Features:
- Built-in call summaries, follow-ups, and Slack alerts
- Handles real phone calls with natural conversation flow
- Can search internal docs and update databases mid-call
- Multiple simultaneous calls capability
- Automatic conversation logging and database updates
Pros:
- No-code platform with visual flow builder
- Real phone call capabilities with natural conversation
- Built-in integrations (Slack, databases, knowledge base)
- Handles multiple concurrent calls
Cons:
- Call features not included in free plan
- Needs paid phone number for call features
Pricing:
- Free plan: 400 tasks/month, 1M character knowledge base
- Pro ($49.99/month): 5,000 tasks/month, access to call features, 20M character knowledge base
- Business ($299.99/month): 30,000 tasks/month, premium phone call automation, priority support
2. Vapi - Best for omnichannel support
What does it do? Vapi is a developer-focused voice AI platform that creates highly customizable voice agents.
Who is it for? Particularly suited for businesses that need deep customization, integration with existing systems, and want to handle high volumes of concurrent calls.
Key Features:
- API-first approach with deep flexibility
- Real-time call handling with impressively low latency
- Use your own models for speech, transcription, and LLMs
- Scales easily to over a million concurrent calls
- Route calls, handle interruptions mid-sentence, pass context to external APIs
Pros:
- Made for developers with great flexibility and full control over logic
- Real-time call handling with impressively low latency
- API-first setup that fits cleanly into modern stacks
- Scales easily to over a million concurrent calls
Cons:
- You'll need to handle your own frontend and call logic
- Not beginner-friendly, requires coding and API knowledge
- Costs can add up quickly for high-volume use cases
Pricing:
- Free trial: $10 in free credits when you sign up
- Platform fee: $0.05/minute (billed per second)
- Phone numbers: $2/month
- Additional costs: Based on usage of third-party models (e.g. OpenAI, ElevenLabs)
Key Providers
ElevenLabs - Best for expressive AI voices What does it do? ElevenLabs is a voice generation platform that specializes in producing incredibly lifelike, emotionally rich speech.
Who is it for? Perfect for teams who are already building AI voice agents and want them to sound genuinely human.
- Exceptionally lifelike, emotional speech synthesis
- Voice cloning and multi-language support
- API-first approach (requires pairing with agent logic)
- Free plan available, paid from $5/mo
PlayHT - Best for lifelike conversations
- Real-time, human-like speech with strong NLP
- Multi-language support and easy business integration
OpenAI Voice Agent SDK - Best for end-to-end automation
- Complete agent SDK with whisper-1 (STT) and tts-1 (TTS)
- Context management and workflow handoffs
Retell AI - Best for full voice agent platform
- Build, test, deploy, and monitor production agents
- SIP integration with pay-as-you-go pricing ($0.07/min)
Plivo - Best for customizable business agents
- Choose your LLM/TTS with real-time response (30ms)
- 99.99% uptime, integrates with OpenAI/ElevenLabs ($0.003/min per stream)
Deepgram - Best for speech-to-text & analysis
- Fast, accurate STT with real-time transcription
- Multi-language support and flexible API
Traditional Telephony: Twilio, Vonage, MessageBird
- Global coverage with call control, TTS, STT, analytics
- Strong developer ecosystem for programmable voice
Quick Recommendations
- Overall best: Lindy (no-code, full-featured)
- Developer-focused: Vapi (highly customizable, API-first)
- Voice quality: ElevenLabs or PlayHT
- End-to-end platform: OpenAI SDK, Retell AI, or Plivo
- Speech recognition: Deepgram
- Telephony infrastructure: Twilio, Vonage, or Plivo
All platforms offer robust APIs and documentation for deploying advanced voice agents in 2025.
Provider | Best For | Key Features | Pricing/Notes |
---|---|---|---|
ElevenLabs | Expressive, emotional voice synthesis | Exceptionally lifelike, emotional voices; supports many languages; voice cloning; API-first | Free plan; paid from $5/mo; requires pairing with agent logic tools |
PlayHT | Lifelike conversations | Real-time, human-like speech; strong NLP; multi-language; easy integration for business use | See provider for pricing |
OpenAI Voice Agent SDK | Conversational logic & workflow automation | End-to-end agent SDK; "whisper-1" for STT, "tts-1" for TTS; context management; easy handoffs | See provider for pricing |
Retell AI | Full voice agent platform | Build, test, deploy, and monitor production-ready agents; SIP integration; pay-as-you-go pricing | $0.07/min, no platform fees |
Plivo | Customizable business voice agents | Choose LLM/TTS; real-time response (30ms); 99.99% uptime; easy integration (OpenAI, ElevenLabs) | $0.003/min per stream |
Deepgram | Speech-to-text & voice analysis | Fast, accurate STT; supports many languages; real-time transcription; flexible API | See provider for pricing |
AgentStation | Custom agent logic with LLMs | Build agents using GPT-4, integrate with Twilio/SignalWire; high customization | See provider for pricing |
Infobip | Voice, IVR, and call routing | Voice calls, IVR, call recording, multi-channel messaging; high customization | From $0.002/min |
Twilio, Vonage, MessageBird | Telephony & programmable voice | Global coverage; call control, TTS, STT, analytics; strong developer ecosystem | See provider for pricing |