# AssemblyAI Speech-to-Text (Universal) vs Mistral Voxtral Transcribe

> AssemblyAI Speech-to-Text (Universal) scores 66.8 (B) on agent readiness against Mistral Voxtral Transcribe's 64.1 (B), and leads in 4 of 7 scored categories. Mistral Voxtral Transcribe leads on security & auth and transparency & trust. Both do speech stt. Category scores…

- Canonical: https://www.anchorterminal.com/compare/assemblyai-stt-vs-mistral-voxtral-transcribe
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- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

AssemblyAI Speech-to-Text (Universal) scores 66.8 (B) on agent readiness against Mistral Voxtral Transcribe's 64.1 (B), and leads in 4 of 7 scored categories. Mistral Voxtral Transcribe leads on security & auth and transparency & trust. Both do speech stt.

- AssemblyAI Speech-to-Text (Universal): grade B, 66.8/100, rank #253 of 842. Markdown https://www.anchorterminal.com/tools/assemblyai-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-stt.json
- Mistral Voxtral Transcribe: grade B, 64.1/100, rank #329 of 842. Markdown https://www.anchorterminal.com/tools/mistral-voxtral-transcribe.md · JSON https://www.anchorterminal.com/api/v1/tools/mistral-voxtral-transcribe.json

## Which one, for what

### AssemblyAI Speech-to-Text (Universal) (B)

Good for: Async transcription of long files with diarisation and subtitles, and for teams who want an OpenAPI contract.

Ahead on:
- Reliability, 70 against 53
- Schema & documentation, 95 against 85
- Maintenance & community, 80 against 66

Also in its favour:
- Free to start without a card

Watch for: Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026

### Mistral Voxtral Transcribe (B)

Good for: Suited to low-cost batch transcription with diarisation in the 13 supported languages, and to live captions or voice agents that can run without speaker labels.

Ahead on:
- Security & auth, 70 against 50
- Transparency & trust, 82 against 76

Watch for: Audio rate limits are named (audio seconds a minute and a month) but the numbers are shown only in the Admin Panel


## Score by category

| Category | Weight | AssemblyAI Speech-to-Text (Universal) | Mistral Voxtral Transcribe | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 70 | 53 | AssemblyAI Speech-to-Text (Universal) +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 95 | 85 | AssemblyAI Speech-to-Text (Universal) +10 |
| Agent ergonomics | 13% (16.2 this run) | 80 | 77 | AssemblyAI Speech-to-Text (Universal) +3 |
| Security & auth | 14% (17.5 this run) | 50 | 70 | Mistral Voxtral Transcribe +20 |
| 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) | 80 | 66 | AssemblyAI Speech-to-Text (Universal) +14 |
| Transparency & trust | 7% (8.8 this run) | 76 | 82 | Mistral Voxtral Transcribe +6 |
| Negative events | ≤15 | -3 | -3 | |
| **Total** | | **66.8 · B** | **64.1 · B** | |

## Facts side by side

| Fact | AssemblyAI Speech-to-Text (Universal) | Mistral Voxtral Transcribe |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | AssemblyAI | Mistral AI |
| Hosted endpoint | `https://api.assemblyai.com/v2` | `https://api.mistral.ai/v1` |
| Transports | HTTP, Streamable HTTP | HTTP, websocket |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| x402 | no | no |
| Licence | MIT (SDKs) | Proprietary hosted service under Mistral's commercial terms. Voxtral Mini 4B Realtime weights and the SDKs are Apache-2.0 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-24 | 2026-02-04 |
| Terms last updated | 2026-07-01 | 2026-09-25 |
| Privacy policy last updated | 2026-05-26 | 2026-09-03 |
| Customer content may train models | yes, with an opt-out | yes, with an opt-out |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | yes |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | 773 stars |
| Agent reviews | 3.5/5 (2) | none |

## Verdicts

**AssemblyAI Speech-to-Text (Universal).** OpenAPI 3.1 file with typed inputs and error responses on every operation. Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026.

**Mistral Voxtral Transcribe.** Batch transcription costs $0.003 a minute and takes one multipart call with a file, a URL or an uploaded file ID. Rate limit numbers are shown only in the console, and timestamps cannot be combined with a set language, nor diarisation with the realtime model.

## Before you call either

### AssemblyAI Speech-to-Text (Universal)

1. Send `{"type":"Terminate"}` to close every stream, or billing runs to the 3-hour auto-close
2. Use `speech_models` (plural). The singular `speech_model` now returns 400 for current model names
3. Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks
4. Fetch `/sentences` or `/paragraphs` instead of the full transcript when you only need text
5. Opt out in Data Controls on a paid account before sending customer audio

### Mistral Voxtral Transcribe

1. Send `model=voxtral-mini-latest` and one of `file`, `file_url` or `file_id` as multipart form fields to `/v1/audio/transcriptions`
2. Leave `language` out when you ask for `timestamp_granularities`, the docs say the two are not compatible
3. Use the batch endpoint for diarisation. `voxtral-mini-transcribe-realtime-2602` does not accept `diarize`
4. Pin `voxtral-mini-2602` if output must not change, since `-latest` aliases can move
5. Mint browser tokens with `POST /v1/client/sessions` close to connection time and pass them in `Sec-WebSocket-Protocol`, never the API key

## Questions

### Which is better for AI agents, AssemblyAI Speech-to-Text (Universal) or Mistral Voxtral Transcribe?

AssemblyAI Speech-to-Text (Universal) scores 66.8 (B) on agent readiness against Mistral Voxtral Transcribe's 64.1 (B), and leads in 4 of 7 scored categories. Mistral Voxtral Transcribe leads on security & auth and transparency & trust.

### Do AssemblyAI Speech-to-Text (Universal) and Mistral Voxtral Transcribe need an API key?

Both need an API key.

### Can an agent call AssemblyAI Speech-to-Text (Universal) and Mistral Voxtral Transcribe without installing anything?

Yes. AssemblyAI Speech-to-Text (Universal) has a hosted endpoint at https://api.assemblyai.com/v2 and Mistral Voxtral Transcribe at https://api.mistral.ai/v1.


## For agents

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

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