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Use cases · Realtime Voice Agent APIs

Best Bring-Your-Own-Model Voice Agent Platforms

Composable voice-agent platforms that let you plug in your own LLM, speech-to-text, and text-to-speech provider keys.

Required capability: BYO models.

Our pick: ElevenLabs Conversational AI (ElevenAgents)

ElevenLabs Conversational AI (ElevenAgents) is a real-time voice agent platform for building inbound and outbound phone automation, covering use cases from customer support and appointment scheduling to healthcare answering services and sales calls. Pricing starts at $0.08 per minute with a free tier of 15 minutes per month, scaling through self-serve plans up to enterprise; telephony costs are billed separately. The platform holds SOC 2 Type 2, HIPAA, GDPR, ISO 27001, and PCI DSS certifications, with SDKs for Python, TypeScript, React, React Native, and Kotlin, plus an MCP server and support for bring-your-own LLM and voice.

Best for: Prototypes and side projects - free to start, no sales call; Regulated or enterprise workloads - compliance attestations and an enterprise plan; AI agents and automation - an agent-ready surface (MCP / llms.txt).

ElevenLabs Conversational AI (ElevenAgents) profile →

Best for…

Best overall
ElevenLabs Conversational AI (ElevenAgents) - our default pick: strongest across pricing, trust and breadth
Best free pick
ElevenLabs Conversational AI (ElevenAgents) - free tier: Free plan at $0/month includes 15 minutes of agent calls per month, up to 4 concurrent ca…
Best for enterprise
ElevenLabs Conversational AI (ElevenAgents) - for regulated or large teams: SOC 2 Type II, HIPAA, enterprise plan
Cheapest to start
Pipecat Cloud (Daily) - from $0.01 minute to start; compare on your real usage, not the entry price
Best for agents
ElevenLabs Conversational AI (ElevenAgents) - easiest to wire up programmatically: MCP server + llms.txt
Broadest surface
Retell AI - 29 documented actions; breadth isn't quality, but it's the most to build on

Ranked (11)

  • #1 ElevenLabs Conversational AI (ElevenAgents)

    81 / 100
    • Best overall
    • Best free pick
    • Best for enterprise
    • Best for agents

    ElevenLabs Conversational AI (ElevenAgents) is a real-time voice agent platform for building inbound and outbound phone automation, covering use cases from customer support and appointment scheduling to healthcare answering services and sales calls. Pricing starts at $0.08 per minute with a free tier of 15 minutes per month, scaling through self-serve plans up to enterprise; telephony costs are billed separately. The platform holds SOC 2 Type 2, HIPAA, GDPR, ISO 27001, and PCI DSS certifications, with SDKs for Python, TypeScript, React, React Native, and Kotlin, plus an MCP server and support for bring-your-own LLM and voice.

    PricingHybrid · from $0.08 minute · free tier ✓
    TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001 · PCI DSS
    Does
    • Outbound calling
    • BYO models
    • Multilingual
    Used byRevolut, Deliveroo, Epic Games, Deutsche Telekom

    ElevenLabs Conversational AI (ElevenAgents) profile →

  • #2 Telnyx Voice AI Agents

    78 / 100

    Telnyx Voice AI Agents is a carrier-grade platform for building inbound and outbound voice AI, covering customer support automation, appointment scheduling, healthcare, and call center use cases across 45+ countries. Pricing is usage-based at $0.05 per minute with self-serve signup and no sales call required. The platform supports bring-your-own LLM and voice, function calling, SIP trunking, and SDKs for Node.js, Python, PHP, Java, Ruby, and Go. It holds SOC 2 Type II, HIPAA, GDPR, ISO 27001, and PCI DSS certifications, and customers include Dialpad, Alibaba, and Grupo Bimbo.

    PricingUsage · from $0.05 minute · free tier ✗
    TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001 · PCI DSS
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • Multilingual
    Used byDialpad, Alibaba, AudioCodes, UJET
    Avoid ifYou want to try it free before paying

    Telnyx Voice AI Agents profile →

  • #3 Twilio ConversationRelay

    76 / 100

    Twilio ConversationRelay is a WebSocket-based orchestration layer that handles speech recognition, text-to-speech, and real-time conversation flow for AI voice agents over PSTN, SIP, and WebRTC, supporting bring-your-own LLM and voice providers. It targets developers building inbound and outbound call automation, such as customer support, appointment scheduling, and live agent escalation. Pricing starts at $0.07 per minute for the orchestration layer, billed separately from underlying voice costs, with self-serve signup and SDKs for seven languages. The service reached general availability in May 2025 and holds SOC 2 Type II, HIPAA, GDPR, ISO 27001, and PCI DSS certifications, though HIPAA coverage requires a Security or Enterprise Edition account.

    PricingUsage · from $0.07 minute · free tier ✗
    TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001 · PCI DSS
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • Multilingual
    Used byOhMD, Scorpion
    Avoid ifYou want to try it free before paying

    Twilio ConversationRelay profile →

  • #4 Vapi

    75 / 100

    Vapi is a voice agent platform for building and deploying AI-powered phone agents handling inbound calls, outbound dialing, appointment scheduling, and lead qualification. Pricing is usage-based at $0.05 per minute with self-serve signup and no sales call required, plus an enterprise plan for custom concurrency. The REST API supports bring-your-own LLM and voice providers, ships SDKs for over ten languages and runtimes including mobile, and holds SOC 2 Type 2, HIPAA, GDPR, and PCI DSS certifications, with customers including New York Life and Intuit.

    PricingUsage · from $0.05 minute · free tier ✓
    TrustSOC 2 Type II · HIPAA · GDPR · PCI DSS
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • Multilingual
    Used byAmazon Ring, Kavak, Instawork, New York Life

    Vapi profile →

  • #5 Cartesia Line

    79 / 100

    Cartesia Line is a telephony platform for building and deploying AI voice agents, supporting inbound call handling, outbound calling, batch dialing, SIP trunking, and real-time conversation via a WebSocket API. It targets developers and businesses automating customer support or voice workflows, with customers including ServiceNow, Vapi, LiveKit, and Replicant. Pricing starts at $0.06 per minute with a free tier of 8 concurrent calls and 20,000 credits per month; enterprise plans are available. The platform holds SOC 2 Type 2, HIPAA, GDPR, and PCI DSS certifications, and ships SDKs for Python and JavaScript/TypeScript.

    PricingHybrid · from $0.06 minute · free tier ✓
    TrustSOC 2 Type II · HIPAA · GDPR · PCI DSS
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • No-code builder
    Used byServiceNow, Maven AGI, Retell, Vapi

    Cartesia Line profile →

  • #6 Pipecat Cloud (Daily)

    64 / 100
    • Cheapest to start

    Pipecat Cloud is a managed hosting platform from Daily for deploying and scaling Pipecat voice AI agents in production, supporting inbound and outbound telephony via PSTN/SIP, WebRTC, and WhatsApp. It targets teams building customer support bots, IVR systems, and outbound call automation, with self-serve signup and usage-based pricing starting at $0.01 per minute. The platform spans four regions, offers Python and JavaScript SDKs with MCP server support, and holds SOC 2 Type 2, ISO 27001, HIPAA, and GDPR certifications. Notable users include NVIDIA, Descript, and Epic.

    PricingUsage · from $0.01 minute · free tier ✗
    TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    Used byNVIDIA, Mercor, Descript, Epic
    Avoid ifYou want to try it free before paying

    Pipecat Cloud (Daily) profile →

  • #7 LiveKit Agents

    71 / 100

    LiveKit Agents is a developer platform for building and deploying realtime voice and video AI agents, supporting inbound and outbound telephony, SIP trunking, multi-agent orchestration, and bring-your-own LLM, STT, and TTS integrations. Pricing starts at $0.01 per minute with a free tier of 1,000 agent session minutes per month and no credit card required, scaling through tiered plans up to custom enterprise arrangements. SDKs are available for Python, Node.js, and Go, and the platform holds SOC 2 Type 2, HIPAA, and GDPR certifications, with HIPAA compliance restricted to Scale and Enterprise plans. Customers include OpenAI, Salesforce, Oracle, and Deutsche Telekom.

    PricingHybrid · from $0.01 minute · free tier ✓
    TrustSOC 2 Type II · HIPAA · GDPR
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • Self-hosted
    • No-code builder
    Used byOpenAI, Oracle, Salesforce, Deutsche Telekom

    LiveKit Agents profile →

  • #8 Deepgram Voice Agent API

    68 / 100

    Deepgram Voice Agent API is a single WebSocket-based interface for building real-time voice AI agents, covering inbound and outbound telephony, function calling, interruption handling, and multi-agent orchestration, with SDKs for Python, Node.js, Go, and C#/.NET. Pricing is usage-based at $0.075 per minute with a one-time $200 trial credit and self-serve signup, scaling to enterprise plans with 100 or more concurrent connections. The platform holds SOC 2 Type 2, HIPAA, GDPR, and PCI DSS certifications and reached general availability in June 2025, with customers including NASA, IBM, Five9, and Aircall. Telephony requires Twilio or Amazon Connect for PSTN access, and the Growth plan carries a $4,000 per year minimum commitment.

    PricingUsage · from $0.07 minute · free tier ✗
    TrustSOC 2 Type II · HIPAA · GDPR · PCI DSS
    Does
    • Outbound calling
    • BYO models
    • Multilingual
    Used byAircall, Jack in the Box, OpenPhone, NASA
    Avoid ifYou want to try it free before paying

    Deepgram Voice Agent API profile →

  • #9 Retell AI

    68 / 100
    • Broadest surface

    Retell AI is a voice agent platform for automating phone calls, supporting both inbound and outbound use cases such as customer support, appointment booking, lead qualification, and call center operations. Pricing is usage-based at $0.055 per minute with a $10 free credit on signup, and an enterprise plan is available for higher-volume needs. The REST API supports bring-your-own LLM and voice, SIP trunking, WebRTC web calling, and function calling, with SDKs for Python, Node.js, and browser JavaScript. The platform holds SOC 2 Type II certification and is HIPAA and GDPR compliant, though it currently operates only from US-based infrastructure.

    PricingUsage · from $0.06 minute · free tier ✗
    TrustSOC 2 Type II · HIPAA · GDPR
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    Used byLenovo, Asbury Auto, Anker, StorageVault
    Avoid ifYou want to try it free before paying

    Retell AI profile →

  • #10 Synthflow AI

    57 / 100

    Synthflow AI is a voice AI platform for automating inbound and outbound phone calls, targeting use cases such as appointment booking, lead qualification, customer support, and healthcare reception. Pricing is usage-based at $0.09 per minute with self-serve signup, no sales call required, and an enterprise plan available. The REST API supports webhooks, warm call transfers, voicemail detection, and sentiment analysis, with HIPAA, GDPR, ISO 27001, and PCI DSS compliance documented. Default PAYG accounts are capped at five concurrent calls, expandable for an additional fee.

    PricingUsage · from $0.09 minute · free tier ✗
    TrustHIPAA · GDPR · ISO 27001 · PCI DSS
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    Used byFreshworks
    Avoid ifYou want to try it free before paying

    Synthflow AI profile →

  • #11 Vocode

    53 / 100

    Vocode is an MIT-licensed open-source library for building real-time voice agents, covering inbound and outbound telephony, IVR navigation, call transfer, answering machine detection, and function calling. It targets developers building AI phone agents for call centers, customer support, appointment booking, and sales. Paid plans start at $25 per seat per month with a free tier included, though the hosted API appears discontinued and active development has stalled since mid-2024. SDKs are available for Python and Node.js, with REST API access authenticated via API key.

    PricingUsage · free tier ✓
    Does
    • Built-in telephony
    • Outbound calling
    • BYO models
    • Self-hosted
    Avoid ifYou need transparent pricing up front

    Vocode profile →

Scope: only APIs with the required capability, picked from published, cited data. The score is one input, not the verdict, and we lead with each one’s trade-off. No reviews yet, no paid placement. See the full Realtime Voice Agent APIs directory.