Features, pricing, and fit
Compare ConversationRelay and Realtime API on voice capabilities, pricing, and fit.
Compare Twilio ConversationRelay and OpenAI Realtime for AI phone agents, Voice AI platforms, then match channels, workflows, and deployment models to your call flow.
Programmable Voice component that connects a TwiML ConversationRelay session to an application WebSocket for STT/TTS, language settings, DTMF, and call events.
Developers building their own voice-agent logic while keeping telephony, media handling, and call control in Twilio.
Explore its buying criteria: AI phone agents · Voice AI platforms.
Model-level realtime API for text and audio input/output over WebRTC, WebSocket, or SIP, with function calling.
Product and engineering teams building a spoken application around a realtime model instead of a packaged contact-center product.
Explore its buying criteria: AI phone agents · Voice AI platforms.
Both profiles checked 2026-09-04.
Use the table below to compare each provider’s documented scope.
Before you decide
Twilio ConversationRelay: Usage-based Programmable Voice minutes and phone numbers, plus ConversationRelay per-minute charges; model, provider, and other call features are separate. OpenAI Realtime: Token-based API pricing for text, audio, and image modalities; audio input/output rates are published per million tokens. Ask both vendors to quote the same expected workload, required channels, and implementation scope. Include required subscriptions and usage charges before comparing the total; the listed starting prices alone may cover different work.
The recorded knowledge and data sources for Twilio ConversationRelay include Not publicly documented. For OpenAI Realtime, they include Not publicly documented. Ask each provider to demonstrate access for the exact systems you use, with permissions, freshness, and failure behavior. A source missing from this directory is not proof that a provider cannot support it.
Use the same representative calls, approved instructions, and escalation rules in both pilots. How does it handle interruption and uncertainty? Which actions can it complete, and which require approval? What context reaches a human during transfer? Record conversation quality, completed tasks, human handoffs, and total cost in the buyer worksheet. Check these specific cautions before launch: Twilio ConversationRelay: Not a packaged agent. Region, carrier, recording, compliance, model, and application responsibilities remain with the implementer. OpenAI Realtime: Not a turnkey contact center. Implement telephony operations, identity, tools, monitoring, evaluation, retention, and escalation.
Record your requirements and pilot results in the buyer worksheet →
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| Criterion | ConversationRelay | Realtime API |
|---|---|---|
| Provider type | Telephony voice-agent runtime | Native realtime multimodal model API |
| Best fit | Developers building their own voice-agent logic while keeping telephony, media handling, and call control in Twilio. | Product and engineering teams building a spoken application around a realtime model instead of a packaged contact-center product. |
| Key capabilities | phone audio streaming; speech interface; interruptions; WebSocket protocol; TwiML controls | audio-to-audio conversation; WebRTC; WebSocket; SIP; tools |
| Team sizes | startup; mid-market; enterprise; developer | startup; mid-market; enterprise; developer |
| Call surfaces | phone / PSTN; WebSocket | WebRTC; WebSocket; SIP; API / SDK |
| Voice stack | Cascaded speech interface with developer-supplied LLM | Native audio input/output with tool calling |
| Telephony | Twilio Programmable Voice; phone numbers; SIP | SIP connection; carrier integration remains buyer responsibility |
| Call controls | Not publicly documented | Not publicly documented |
| Languages | Not publicly documented | Not publicly documented |
| Integrations | Not publicly documented | Not publicly documented |
| Knowledge and data | Not publicly documented | Not publicly documented |
| Pricing model | Usage-based Programmable Voice minutes and phone numbers, plus ConversationRelay per-minute charges; model, provider, and other call features are separate. | Token-based API pricing for text, audio, and image modalities; audio input/output rates are published per million tokens. |
| Pricing signal | ConversationRelay $0.07/min; US local outbound $0.014, inbound $0.0085, SIP $0.004, number $1.15/month. | GPT-Realtime audio $32 per million input audio tokens and $64 per million output audio tokens. |
| Free plan or trial | Not publicly documented | Not publicly documented |
| What stands out | ConversationRelay handles the live call’s STT/TTS and session transport, then sends prompts, audio-control events, and optional DTMF over a required secure WebSocket to the application. | GPT-Realtime accepts and returns audio directly, while the Agents SDK supplies transport helpers plus tools, guardrails, handoffs, and session history. |
| Considerations | Not a packaged agent. Region, carrier, recording, compliance, model, and application responsibilities remain with the implementer. | Not a turnkey contact center. Implement telephony operations, identity, tools, monitoring, evaluation, retention, and escalation. |
Developers building their own voice-agent logic while keeping telephony, media handling, and call control in Twilio.
ConversationRelay handles the live call’s STT/TTS and session transport, then sends prompts, audio-control events, and optional DTMF over a required secure WebSocket to the application.
Product and engineering teams building a spoken application around a realtime model instead of a packaged contact-center product.
GPT-Realtime accepts and returns audio directly, while the Agents SDK supplies transport helpers plus tools, guardrails, handoffs, and session history.
Verify current pricing, limits, security, and required integrations directly with each provider before purchasing.
Twilio ConversationRelay handles call speech recognition and speech output, then exchanges text and events with your application over a secure WebSocket. Your application chooses the language model and executes business logic and tools. An OpenAI text model can be part of that application without using the Realtime API.
OpenAI Realtime supports audio conversations over WebRTC, WebSocket or SIP. When comparing it with ConversationRelay, identify how your design connects callers to the model and who owns call control, tools and session recovery. Compare an actual carrier path and the same business task before selecting the stack.
For either design, list carrier and number charges, model usage, speech or relay charges, hosting and monitoring. Test interrupted responses, an unavailable business system and a failed human transfer. Measure completed tasks and repeat calls alongside latency and total cost.
Test recognition, speech quality, interruptions, language switching, tool use, and human transfer with your own calls in the required language. Availability can vary by model, plan, and phone route.
DocsBot documents multilingual voice workflows and Japanese support. Verify the exact voice, phone path, and transfer behavior in your pilot. Review DocsBot language information ↗
Other providers’ language claims reflect cited vendor material; confirm Japanese and other required languages directly with each provider.
Listing does not imply endorsement or a performance guarantee. This directory is published by DocsBot. Editorial policy
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