Features, pricing, and fit
Compare Retell AI and Synthflow on voice capabilities, pricing, and fit.
Compare Retell AI and Synthflow for AI phone agents, then match channels, workflows, and deployment models to your call flow.
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.
No-code voice-agent builder with configurable voice engines, imported or cloned voices, and an enterprise fallback voice model.
Teams wanting visual call-flow construction and voice-provider controls with deployment pricing scoped by usage, telephony, integrations, and support.
Explore its buying criteria: AI phone agents · AI receptionists · Conversation builders.
Both profiles checked 2026-09-04.
Use the table below to compare each provider’s documented scope.
Before you decide
Retell AI: Pay-as-you-go per-minute component pricing with optional add-ons; Enterprise uses custom volume pricing and terms. Synthflow: Sales-led account pricing scoped to expected usage, telephony, integrations, security, and launch support. 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 Retell AI include Not publicly documented. For Synthflow, 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: Retell AI: Component rates may not equal complete cost. Confirm concurrency, premium model/voice, transfer, storage, QA, and carrier charges. Synthflow: Confirm current architecture, availability, call controls, data handling, language coverage, and complete cost in a scoped pilot.
Record your requirements and pilot results in the buyer worksheet →
Swipe or scroll the table to see every column.
| Criterion | Retell AI | Synthflow |
|---|---|---|
| Provider type | Voice agent platform | No-code voice agent builder |
| Best fit | Teams comparing a managed agent builder with both visual flow design and API/SDK control. | Teams wanting visual call-flow construction and voice-provider controls with deployment pricing scoped by usage, telephony, integrations, and support. |
| Key capabilities | inbound and outbound agents; flow builder; testing; analytics; functions; SIP | visual builder; templates; booking; transfers; white label; analytics |
| Team sizes | startup; mid-market; enterprise; developer | small; mid-market; enterprise; agencies and integrators |
| Call surfaces | phone / PSTN; API / SDK | phone / PSTN; API / SDK |
| Voice stack | Configurable STT-LLM-TTS pipeline with custom LLM option | Cascaded STT-LLM-TTS pipeline |
| Telephony | managed numbers; SIP trunking; bring-your-own telephony | Not publicly documented |
| 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 | Pay-as-you-go per-minute component pricing with optional add-ons; Enterprise uses custom volume pricing and terms. | Sales-led account pricing scoped to expected usage, telephony, integrations, security, and launch support. |
| Pricing signal | 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. | Sales-led; no current public production rate. |
| Free plan or trial | Not publicly documented | Not publicly documented |
| What stands out | 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. | Synthflow’s voice editor supports built-in, third-party, imported, and cloned voices, with an Enterprise fallback provider setting for calls. |
| Considerations | Component rates may not equal complete cost. Confirm concurrency, premium model/voice, transfer, storage, QA, and carrier charges. | Confirm current architecture, availability, call controls, data handling, language coverage, and complete cost in a scoped pilot. |
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.
Teams wanting visual call-flow construction and voice-provider controls with deployment pricing scoped by usage, telephony, integrations, and support.
Synthflow’s voice editor supports built-in, third-party, imported, and cloned voices, with an Enterprise fallback provider setting for calls.
Verify current pricing, limits, security, and required integrations directly with each provider before purchasing.
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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