Features, pricing, and fit
Compare ConversationRelay and Retell AI on voice capabilities, pricing, and fit.
Compare Twilio ConversationRelay and Retell AI 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.
Hosted voice and chat agent platform built around either node-based conversation flows or single prompts, with telephony, tools, knowledge base, and analytics.
Teams comparing a managed agent builder with both visual flow design and API/SDK control.
Explore its buying criteria: AI phone agents · Voice AI platforms · Voice evaluation and observability.
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. Retell AI: Pay-as-you-go per-minute component pricing with optional add-ons; Enterprise uses custom volume pricing and terms. 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 Retell AI, 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. Retell AI: Component rates may not equal complete cost. Confirm concurrency, premium model/voice, transfer, storage, QA, and carrier charges.
Record your requirements and pilot results in the buyer worksheet →
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| Criterion | ConversationRelay | Retell AI |
|---|---|---|
| Provider type | Telephony voice-agent runtime | Voice agent platform |
| Best fit | Developers building their own voice-agent logic while keeping telephony, media handling, and call control in Twilio. | Teams comparing a managed agent builder with both visual flow design and API/SDK control. |
| Key capabilities | phone audio streaming; speech interface; interruptions; WebSocket protocol; TwiML controls | inbound and outbound agents; flow builder; testing; analytics; functions; SIP |
| Team sizes | startup; mid-market; enterprise; developer | startup; mid-market; enterprise; developer |
| Call surfaces | phone / PSTN; WebSocket | phone / PSTN; API / SDK |
| Voice stack | Cascaded speech interface with developer-supplied LLM | Configurable STT-LLM-TTS pipeline with custom LLM option |
| Telephony | Twilio Programmable Voice; phone numbers; SIP | managed numbers; SIP trunking; bring-your-own telephony |
| 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. | Pay-as-you-go per-minute component pricing with optional add-ons; Enterprise uses custom volume pricing and terms. |
| Pricing signal | ConversationRelay $0.07/min; US local outbound $0.014, inbound $0.0085, SIP $0.004, number $1.15/month. | Vendor range $0.07-$0.31/min; infrastructure $0.055, typical TTS $0.015, telephony $0.015, KB $0.005, guardrails $0.005, PII removal $0.01, and QA $0.10 after 100 minutes. |
| 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. | Retell documents two agent shapes—node-based flows and single prompts—and pairs them with built-in telephony, knowledge, tools, analytics, and MCP/API access. |
| Considerations | Not a packaged agent. Region, carrier, recording, compliance, model, and application responsibilities remain with the implementer. | Component rates may not equal complete cost. Confirm concurrency, premium model/voice, transfer, storage, QA, and carrier charges. |
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.
Teams comparing a managed agent builder with both visual flow design and API/SDK control.
Retell documents two agent shapes—node-based flows and single prompts—and pairs them with built-in telephony, knowledge, tools, analytics, and MCP/API access.
Verify current pricing, limits, security, and required integrations directly with each provider before purchasing.
ConversationRelay supplies the speech interface around a Twilio call. Your WebSocket application chooses the model and owns tools, state and business logic. Choose this route when engineers need that application control and can operate it.
Retell offers a managed agent platform with selectable voice and model components. Its pricing calculator separates infrastructure, voice, LLM and telephony choices. Compare the selected configuration with your complete Twilio stack, including model usage, hosting, carrier charges and maintenance; a headline per-minute rate cannot settle the decision.
Use the same caller task, phone route and business-system integration. Measure end-of-turn to first-audio latency, completed tasks and cost per completed task. Include a slow tool, caller correction, interruption and unavailable transfer destination. Verify the final CRM or calendar record and retry behavior, then record the engineering work each approach requires.
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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