Compare Lab
AssemblyAI vs Retell AI
AssemblyAI is positioned as transcription APIs for live and recorded audio, with model-specific language and analysis options. Retell AI is positioned as a configurable call-agent platform with visual flows, APIs and integrated ca
AssemblyAI is positioned as transcription APIs for live and recorded audio, with model-specific language and analysis options. Retell AI is positioned as a configurable call-agent platform with visual flows, APIs and integrated call operations. Start by deciding who owns the missing layers, then inspect the documented differences below.
STT and Full Platforms are different product categories. An underlying engine or framework is not a complete substitute for a deployed agent workflow.
18 jointly documented catalog fields. This measures evidence coverage, not equivalent quality or an overall winner.
Test opening hours, booking conflicts and an unanswered transfer.
Start where the records differ.
Values and evidence states are compared together. Shared facts follow the differences; Unknown never means No.
| Decision point | AssemblyAI | Retell AI |
|---|---|---|
| Billing unitDifferent records | Async audio hours; streaming connection hours; agent session minutes; gateway tokens | minute |
| Warm transferDifferent records | Unknown | Yes |
| HIPAA pathDifferent records | Yes | Yes |
| WebhooksDifferent records | YesUnknown | YesAPI / webhook |
| Billing modelShared state | component-stack | component-stack |
| Bring your telephonyShared state | Yes | Yes |
Your requirements & next steps
Your requirements
Ready-made / AI receptionist · Strict evidence mode
No personal requirements yet. Add criteria in Advanced Filter to prioritize this comparison.
STT hours/session duration, agent minutes, gateway tokens and add-ons remain distinct.
Reviewed current public offer; retain original billing scope and units.
Model rates are scoped; add-ons stack; reference states updated May 29, 2026 and conflicts are retained.
Reviewed current public offer; retain original billing scope and units.
Idle streaming connection duration is billable. No fabricated all-in phone cost per minute.
Reviewed current public offer; retain original billing scope and units.
SSO costs $199 per connection per month; do not mistake no base fee for no fixed optional charges.
Zero platform fee is not zero total fixed cost.
Not a fixed monthly audio allowance; credits do not expire.
Paid extras$8/slot/month and$8/KB/month; usage separate.
No invented bundle overage.
Reviewed current public offer; retain original billing scope and units.
Component choices and call mix must be specified.
Reviewed current public offer; retain original billing scope and units.
Not yet researched against this buyer-critical field standard.
Reviewed current public offer; retain original billing scope and units.
No complete phone bill ceiling from minutes alone; carrier, model and addon scope vary.
A headline configuration range is not a ceiling on telephony, model, add-on or burst charges.
No complete phone bill ceiling from minutes alone; carrier, model and addon scope vary.
Research conclusion about cost completeness, not a vendor capability.
Anyone with this link can view the encoded decision criteria.
Vendor documentation establishes a claim. Public model benchmarks are separate context, not measurements of these platforms.
Open saved comparison ↗What to verify together.
AssemblyAI
A transcription hour is not a complete agent hour.
Universal-2 async / Universal-Streaming $0.15/hour; U3.5 Pro async $0.21/hour; U3 realtime $0.45/hour; Voice Agent $0.075/min · V3.3 evidence review · Voice Agent API reference; standalone STT is hourly; transport/add-ons separate
Excluded / confirm: Complete cost cannot be established from this reference. No complete phone bill ceiling from minutes alone; carrier, model and addon scope vary. · Twilio carrier; optional custom/Gateway LLM; standalone STT add-ons and per-channel billing
STT hours/session duration, agent minutes, gateway tokens and add-ons remain distinct.
Retell AI
The advertised price band is not a ceiling for every model configuration.
Voice-agent configuration range $0.07–$0.31/min · V3.3 evidence review · Published configured-agent range lower reference; not a guaranteed all-in floor or ceiling
Excluded / confirm: Complete cost cannot be established from this reference. A headline configuration range is not a ceiling on telephony, model, add-on or burst charges. · Telephony, selected LLM/TTS, add-ons and concurrency burst can add charges
Reviewed current public offer; retain original billing scope and units.
The evidence overlap.
Both records have documented values for Product type, Call direction, Technical setup, Pricing model, Published numeric pricing, Bring your telephony, Twilio, Call recording, OpenAI models, Anthropic models, Google models, Bring your model and additional fields shown in Compare. Matching availability does not measure behavior under your call conditions.
Run the same booking, tool failure and unsuccessful human-transfer cases. Record both outcomes and billable units before signing a deployment agreement.
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