# AssemblyAI Voice Agent API vs Gemini Live API

> AssemblyAI Voice Agent scores 64.4 (B) to Gemini Live's 57.1 (C) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live
- Markdown: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.md (~2,800 tokens)
- Slim: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

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.

- AssemblyAI Voice Agent API: grade B, 64.4/100, rank #351 of 950. Markdown https://www.anchorterminal.com/tools/assemblyai-voice-agent.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json
- Gemini Live API: grade C, 57.1/100, rank #622 of 950. Markdown https://www.anchorterminal.com/tools/gemini-live.md · JSON https://www.anchorterminal.com/api/v1/tools/gemini-live.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## 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

| Category | Weight | AssemblyAI Voice Agent API | Gemini Live API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 41 | AssemblyAI Voice Agent API +19 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 66 | AssemblyAI Voice Agent API +17 |
| Agent ergonomics | 13% (16.2 this run) | 72 | 69 | AssemblyAI Voice Agent API +3 |
| Security & auth | 14% (17.5 this run) | 62 | 48 | AssemblyAI Voice Agent API +14 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 64 | 83 | Gemini Live API +19 |
| Transparency & trust | 7% (8.8 this run) | 66 | 72 | Gemini Live API +6 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **64.4 · B** | **57.1 · C** | |

## Facts side by side

| Fact | AssemblyAI Voice Agent API | Gemini Live API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | AssemblyAI, Inc. | Google |
| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `https://generativelanguage.googleapis.com/v1beta` |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| Price for voice agents | $0.075 per minute of call | not published |
| x402 | no | no |
| Licence | Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file | Proprietary service under the Gemini API Additional Terms of Service. The Python and JavaScript SDKs are Apache-2.0 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-08-26 | 2026-09-15 |
| Terms last updated | 2026-07-01 | 2026-04-28 |
| Privacy policy last updated | 2026-05-26 | 2026-10-01 |
| Customer content may train models | yes, with an opt-out | yes |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | yes | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | none | 29.5M 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.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.json, and with the fewest tokens: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "assemblyai-voice-agent", "b": "gemini-live"}`. From a terminal: `anchor compare assemblyai-voice-agent gemini-live`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json and https://www.anchorterminal.com/api/v1/tools/gemini-live.json

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