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OpenAI Realtime API vs Retell AI
OpenAI Realtime API is positioned as speech-to-speech API for developers implementing their own voice application. Retell AI is positioned as a configurable call-agent platform with visual flows, APIs and integrated call operation
OpenAI Realtime API is positioned as speech-to-speech API for developers implementing their own voice application. 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.
Developer Frameworks and Full Platforms are different product categories. An underlying engine or framework is not a complete substitute for a deployed agent workflow.
12 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 | OpenAI Realtime API | Retell AI |
|---|---|---|
| Billing unitDifferent records | 1 million text/audio/image tokens; transcription separately metered | minute |
| Bring your telephonyDifferent records | Yes | Yes |
| Bring your modelDifferent records | Unknown | Yes |
| Warm transferDifferent records | Unknown | Yes |
| HIPAA pathDifferent records | Unknown | Yes |
| WebhooksDifferent records | YesUnknown | YesAPI / webhook |
Your requirements & next steps
Your requirements
Ready-made / AI receptionist · Strict evidence mode
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Realtime model tokens plus input transcription, tools and carrier/hosting; not GPT-Live session-minute billing.
Reviewed current public offer; retain original billing scope and units.
Cached audio/text and image inputs have separate rates. Rate is not per-minute.
Reviewed current public offer; retain original billing scope and units.
Model scope fixed to GPT-Realtime-2, not all voice models.
Reviewed current public offer; retain original billing scope and units.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
Zero platform fee is not zero total fixed cost.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
Paid extras$8/slot/month and$8/KB/month; usage separate.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
Reviewed current public offer; retain original billing scope and units.
Repeated context, cache behavior and turn count affect token charges.
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.
Full bill requires measured model/token/cache/tool/carrier usage; conversation minutes alone are insufficient.
A headline configuration range is not a ceiling on telephony, model, add-on or burst charges.
Full bill requires measured model/token/cache/tool/carrier usage; conversation minutes alone are insufficient.
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.
OpenAI Realtime API
A token rate cannot be compared directly with a bundled call-minute price.
GPT-Realtime-2 audio input $32/M, audio output $64/M; text input $4/M, output $24/M · V3.3 evidence review · GPT-Realtime-2 input audio tokens only; output/audio/text/cache have different rates; not 2.1 rate evidence
Excluded / confirm: Complete cost cannot be established from this reference. Full bill requires measured model/token/cache/tool/carrier usage; conversation minutes alone are insufficient. · Input transcription, tool/backend calls, carrier and application infrastructure
Realtime model tokens plus input transcription, tools and carrier/hosting; not GPT-Live session-minute billing.
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, Technical setup, Pricing model, Published numeric pricing, OpenAI TTS, OpenAI models, MCP tools, Function / tool calling, Interruption controls, Official product documentation, Checked within 30 days, Retained price snapshot. 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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