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Head to head · Voice agents · October 2026 research run

AssemblyAI Voice Agent API vs Gemini Live API

AssemblyAI Voice Agent API scores 64.4 (B) on agent readiness against Gemini Live API's 57.1 (C), and leads in 4 of 7 scored categories. Gemini Live API leads on maintenance & community and transparency & trust. Both do voice agents.

Best conversational voice-agent APIs · All 91 voice agents comparisons

AssemblyAI Voice Agent APIAssemblyAI, Inc. · HTTP API B64.4/100#351 of 950 Gemini Live APIGoogle · HTTP API C57.1/100#622 of 950

Which one, for what

AssemblyAI Voice Agent API B

Good for A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own.

Ahead on

  • Reliability, 60 against 41
  • Schema & documentation, 83 against 66
  • Security & auth, 62 against 48

Also in its favour

  • Free to start without a card

Watch for

No number is published for the concurrent-session limit that the concurrency_exceeded error enforces

Gemini Live API C

Good for Teams building their own voice or vision assistant on a single speech-to-speech model with function calling and Search grounding, who can run a backend for tokens and audio transport.

Ahead on

  • Maintenance & community, 83 against 64
  • Transparency & trust, 72 against 66

Watch for

The WebSocket guide authenticates with the API key as a key query parameter, and ephemeral tokens as an access_token query parameter.

Score by category

CategoryWeight this runAssemblyAI Voice Agent APIGemini Live APIEdge
Reliability16%206041AssemblyAI Voice Agent API +19
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28366AssemblyAI Voice Agent API +17
Agent ergonomics13%16.27269AssemblyAI Voice Agent API +3
Security & auth14%17.56248AssemblyAI Voice Agent API +14
Payments & pricing10%12.54040even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86483Gemini Live API +19
Transparency & trust7%8.86672Gemini Live API +6
Negative events≤1500
Total64.4 · B57.1 · C

Facts side by side

FactAssemblyAI Voice Agent APIGemini Live API
KindHTTP APIHTTP API
VendorAssemblyAI, Inc.Google
Hosted endpointwss://agents.assemblyai.com/v1/wshttps://generativelanguage.googleapis.com/v1beta
TransportsHTTPHTTP
AuthAPI keyAPI key
PricingPay per useFreemium
Price for voice agents$0.075 per minute of callnot published
x402nono
LicenceProprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence fileProprietary service under the Gemini API Additional Terms of Service. The Python and JavaScript SDKs are Apache-2.0
Read-only variant documentednono
llms.txtyesyes
Last release2026-08-262026-09-15
Terms last updated2026-07-012026-04-28
Privacy policy last updated2026-05-262026-10-01
Customer content may train modelsyes, with an opt-outyes
Terms restrict automated accessyesyes
Terms restrict benchmarkingyesyes
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waivernot found in the textnot found in the text
Popularitynone29.5M npm/wk, 34.1M PyPI/wk

Verdicts

AssemblyAI Voice Agent API

One $0.075 a minute rate covers speech-to-text, the managed model, speech output, recordings and hosting, and the socket has an AsyncAPI file, typed error codes and a 30-second resume window. No concurrent-session limit is published, the status page has no Voice Agent component, and phone calls are inbound only through a Twilio trunk the customer owns.

Gemini Live API

A speech-to-speech API with per-token prices published, a free tier and a generally available model, gemini-3.8-live, since 15 September 2026. The documented raw WebSocket connection carries the API key in the URL, connections reset about every 10 minutes, and no SLA or readable incident history was found for the Developer API.

Before you call either

AssemblyAI Voice Agent API

  1. Send session.end before closing the socket. Without it the session stays resumable, and billed, for 30 seconds
  2. Retry only at_capacity, concurrency_exceeded and internal_error, with backoff. Every other session error code is fatal
  3. Send tool.result inside the reply.done handler, not straight after tool.call
  4. Mint a one-time token with GET /v1/token for browser clients and never ship the API key to a page
  5. Deduplicate webhooks on event_id, and verify X-AAI-Signature against the raw body bytes because a 401 is not retried

Gemini Live API

  1. Enable sessionResumption and keep the newest handle. Connections end after about 10 minutes, and handles stay valid for 2 hours.
  2. Set contextWindowCompression with a sliding window. Without it audio sessions stop at 15 minutes and audio with video at 2 minutes, and every turn re-bills the whole context.
  3. On gemini-3.8-live function calls are non-blocking by default. Set behavior: BLOCKING if the model must wait for the tool response.
  4. Send 16 kHz 16-bit PCM in 20 to 40 ms chunks and discard buffered playback when interrupted is true.
  5. Keep the API key on a server and send it through the SDK. Give browsers an ephemeral token from POST /v1beta/auth_tokens, locked with liveConnectConstraints.

Questions

Which is better for AI agents, AssemblyAI Voice Agent API or Gemini Live API?

AssemblyAI Voice Agent API scores 64.4 (B) on agent readiness against Gemini Live API's 57.1 (C), and leads in 4 of 7 scored categories. Gemini Live API leads on maintenance & community and transparency & trust.

Do AssemblyAI Voice Agent API and Gemini Live API need an API key?

Both need an API key.

Can an agent call AssemblyAI Voice Agent API and Gemini Live API without installing anything?

Yes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and Gemini Live API at https://generativelanguage.googleapis.com/v1beta.

Other comparisons with AssemblyAI Voice Agent API or Gemini Live API

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