Features, pricing, and fit
Compare Gemini Live API and Sierra Agent on voice capabilities, pricing, and fit.
Compare Gemini Live and Sierra Agent for AI phone agents, then match channels, workflows, and deployment models to your call flow.
Google's Gemini Live API streams multimodal sessions over WebSockets; its stable native voice-agent models are Gemini 3.8 Live and Gemini 3.8 Live Extended Thinking.
Developers building low-latency conversational agents that need native audio, multimodal input, and function calling in a persistent WebSocket session.
Explore its buying criteria: AI phone agents · Voice AI platforms.
Customer-service agent platform for inbound/outbound voice, messaging, email, live assist, and ChatGPT channel publishing.
CX organizations that want one agent model across voice and digital channels with brand-persona controls.
Explore its buying criteria: AI phone agents · Contact-center AI.
Gemini Live checked 2026-09-28; Sierra Agent checked 2026-09-04.
Use the table below to compare each provider’s documented scope.
Before you decide
Gemini Live: Standard Live API usage is token-metered: $3 per 1M input audio tokens ($0.005/min equivalent) and $12 per 1M output audio tokens ($0.018/min equivalent), plus separate text-token usage. Accumulated session context is billed each turn, so costs can grow with conversation history. Sierra Agent: Outcome-based pricing tied to agreed results; Sierra also describes blended consumption pricing for routing or greeter interactions. 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 Gemini Live include Not publicly documented. For Sierra Agent, 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: Gemini Live: Google labels the Live API preview even though both Gemini 3.8 Live model IDs are stable. Native audio sessions use AUDIO response modality; enable output transcription for text. Audio-only sessions are limited to 15 minutes and audio-plus-video sessions to 2 minutes unless extended with session management. Client-to-server apps need ephemeral tokens. Accumulated audio/context is billed per turn. Sierra Agent: Public voice detail is limited. Confirm telephony, transfer, recording, retention, language, and exact billable outcome.
Record your requirements and pilot results in the buyer worksheet →
Swipe or scroll the table to see every column.
| Criterion | Gemini Live API | Sierra Agent |
|---|---|---|
| Provider type | Native realtime multimodal model API | Enterprise customer-service agent platform |
| Best fit | Developers building low-latency conversational agents that need native audio, multimodal input, and function calling in a persistent WebSocket session. | CX organizations that want one agent model across voice and digital channels with brand-persona controls. |
| Key capabilities | stable native voice-agent models: gemini-3.8-live and gemini-3.8-live-extended-thinking; bidirectional native audio; text, image, and video input; function calling; asynchronous tool execution; session controls and interruption handling | conversations; backend actions; guardrails; analytics; multi-channel deployment |
| Team sizes | startup; mid-market; enterprise; developer | enterprise |
| Call surfaces | WebSocket; server-side applications; client applications using ephemeral tokens | voice; chat; digital customer service |
| Voice stack | Native audio agents: Gemini 3.8 Live (gemini-3.8-live) and Gemini 3.8 Live Extended Thinking (gemini-3.8-live-extended-thinking).; Separate TTS models: gemini-3.8-flash-tts and gemini-3.8-flash-lite-tts generate speech; neither is a Live agent.; Separate transcription endpoints: gemini-3.5-transcribe handles audio files; gemini-3.5-transcribe-live is a Live API speech-to-text mode, not a conversational agent.; Separate translation mode: gemini-3.5-live-translate-preview is a Live API interpreter for 70+ languages, not a conversational agent; it is preview. | Not publicly documented |
| Telephony | Not publicly documented | Not publicly documented |
| Call controls | Not publicly documented | Not publicly documented |
| Languages | The Live API documentation lists Japanese (ja) and multilingual support; native audio output can switch languages naturally in conversation. A supported-language list does not guarantee equivalent call quality. Separately, Transcribe lists Japanese (ja-JP) among 85+ languages; Flash TTS lists 130 languages and Flash-Lite TTS 101 (both include Japanese); Live Translate preview supports 70+ languages. | Not publicly documented |
| Integrations | Not publicly documented | Not publicly documented |
| Knowledge and data | Not publicly documented | Not publicly documented |
| Pricing model | Standard Live API usage is token-metered: $3 per 1M input audio tokens ($0.005/min equivalent) and $12 per 1M output audio tokens ($0.018/min equivalent), plus separate text-token usage. Accumulated session context is billed each turn, so costs can grow with conversation history. | Outcome-based pricing tied to agreed results; Sierra also describes blended consumption pricing for routing or greeter interactions. |
| Pricing signal | Standard paid rates are $0.005/min equivalent for input audio and $0.018/min equivalent for output audio, billed separately plus text tokens; Google also lists a free API tier. | Outcome-based enterprise pricing; no public rate. |
| Free plan or trial | Gemini API free tier listed; paid Live usage is token-metered. | Not publicly documented |
| What stands out | The stable Gemini 3.8 Live models combine native audio dialogue with configurable tool calls over persistent WebSocket sessions; TTS, transcription, and translation are separate supporting models. | Sierra pairs channel-spanning agents and configurable Voice Personas with an outcome-based commercial model whose billing is tied to agreed task results; routing/greeter cases may use consumption pricing. |
| Considerations | Google labels the Live API preview even though both Gemini 3.8 Live model IDs are stable. Native audio sessions use AUDIO response modality; enable output transcription for text. Audio-only sessions are limited to 15 minutes and audio-plus-video sessions to 2 minutes unless extended with session management. Client-to-server apps need ephemeral tokens. Accumulated audio/context is billed per turn. | Public voice detail is limited. Confirm telephony, transfer, recording, retention, language, and exact billable outcome. |
Developers building low-latency conversational agents that need native audio, multimodal input, and function calling in a persistent WebSocket session.
The stable Gemini 3.8 Live models combine native audio dialogue with configurable tool calls over persistent WebSocket sessions; TTS, transcription, and translation are separate supporting models.
CX organizations that want one agent model across voice and digital channels with brand-persona controls.
Sierra pairs channel-spanning agents and configurable Voice Personas with an outcome-based commercial model whose billing is tied to agreed task results; routing/greeter cases may use consumption pricing.
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
Your business. Your shortlist.
Start with your website. Answer a few focused questions, then get a personalized PDF with fit, trade-offs, alternatives and a pilot plan for your call flow.
