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OpenAI Realtime API vs Sierra
OpenAI Realtime API is positioned as speech-to-speech API for developers implementing their own voice application. Sierra is positioned as enterprise customer-service agents spanning voice and other channels, priced around agreed
OpenAI Realtime API is positioned as speech-to-speech API for developers implementing their own voice application. Sierra is positioned as enterprise customer-service agents spanning voice and other channels, priced around agreed outcomes. Start by deciding who owns the missing layers, then inspect the documented differences below.
Developer Frameworks and Enterprise Platforms are different product categories. An underlying engine or framework is not a complete substitute for a deployed agent workflow.
4 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 | Sierra |
|---|---|---|
| Billing modelDifferent records | component-stack | outcome-based |
| Billing unitDifferent records | 1 million text/audio/image tokens; transcription separately metered | Contract-defined successful outcome |
| Bring your telephonyDifferent records | Yes | Unknown |
| HIPAA pathDifferent records | Unknown | Yes |
| WebhooksDifferent records | YesUnknown | UnknownUnknown |
| Bring your modelShared state | Unknown | Unknown |
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.
Payment for specifically agreed valuable outcomes, not uniform minutes.
Cached audio/text and image inputs have separate rates. Rate is not per-minute.
No complete public commercial schedule or definition of billable outcome; minutes cannot determine total.
Model scope fixed to GPT-Realtime-2, not all voice models.
Outcome definition, exceptions and attribution need contract.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
No complete public commercial schedule or definition of billable outcome; minutes cannot determine total.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
No supporting statement located in the bounded official corpus; confirm scope with vendor. Unknown is not No.
Published Realtime token rates do not establish these account/contract terms. GPT-Live duration billing and unrelated fine-tuning discounts must not be imported.
No supporting statement located in the bounded official corpus; confirm scope with vendor. Unknown is not No.
Repeated context, cache behavior and turn count affect token charges.
No supporting statement located in the bounded official corpus; confirm scope with vendor. Unknown is not No.
Not yet researched against this buyer-critical field standard.
Not yet researched against this buyer-critical field standard.
Full bill requires measured model/token/cache/tool/carrier usage; conversation minutes alone are insufficient.
No complete public commercial schedule or definition of billable outcome; minutes cannot determine total.
Full bill requires measured model/token/cache/tool/carrier usage; conversation minutes alone are insufficient.
No complete public commercial schedule or definition of billable outcome; minutes cannot determine total.
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.
Sierra
Agree how an outcome is counted, disputed and audited before comparing costs.
Custom quote / current rate unresolved · V3.3 evidence review · Contract-defined successful outcome; no public numeric quote or uniform per-minute rate
Excluded / confirm: Complete cost cannot be established from this reference. No complete public commercial schedule or definition of billable outcome; minutes cannot determine total. · Provider, carrier and custom contract terms require separate verification
Payment for specifically agreed valuable outcomes, not uniform minutes.
The evidence overlap.
Both records have documented values for Pricing model, MCP tools, 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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