# Azure AI Speech speech-to-text vs Cartesia Ink

> Azure AI Speech speech-to-text scores 73 (BB) to Cartesia Ink's 67.9 (B) for speech-to-text. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/azure-speech-to-text-vs-cartesia-ink-stt
- Markdown: https://www.anchorterminal.com/compare/azure-speech-to-text-vs-cartesia-ink-stt.md (~2,900 tokens)
- Slim: https://www.anchorterminal.com/compare/azure-speech-to-text-vs-cartesia-ink-stt.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
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- Updated: 2026-10-09

Azure AI Speech speech-to-text scores 73 (BB) on agent readiness against Cartesia Ink's 67.9 (B), and leads in 4 of 7 scored categories. Cartesia Ink leads on schema & documentation, payments & pricing and maintenance & community. Both do speech-to-text.

- Azure AI Speech speech-to-text: grade BB, 73/100, rank #93 of 950. Markdown https://www.anchorterminal.com/tools/azure-speech-to-text.md · JSON https://www.anchorterminal.com/api/v1/tools/azure-speech-to-text.json
- Cartesia Ink: grade B, 67.9/100, rank #238 of 950. Markdown https://www.anchorterminal.com/tools/cartesia-ink-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/cartesia-ink-stt.json
- Best speech-to-text APIs for AI agents: https://www.anchorterminal.com/best/speech-to-text/index.md
- All 91 stt comparisons: https://www.anchorterminal.com/compare/speech-to-text/index.md

## Which one, for what

### Azure AI Speech speech-to-text (BB)

Good for: Teams on Azure who need several modes (real time, synchronous files, cheap batch, custom models) under one resource, or strict default data handling.

Ahead on:
- Reliability, 80 against 73
- Security & auth, 85 against 52
- Transparency & trust, 85 against 67

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: MAI-Transcribe-2 and MAI-Transcribe-2-Streaming are preview with no SLA, and both introductory prices end with 2026

### Cartesia Ink (B)

Good for: Suited to voice agents that need turn detection and transcription from one model in English, French, Hindi, Japanese or Spanish, and to teams already using Cartesia text-to-speech.

Ahead on:
- Schema & documentation, 89 against 80
- Payments & pricing, 35 against 20
- Maintenance & community, 85 against 80

Watch for: The terms let Cartesia train models on inputs and outputs unless otherwise agreed. Opting out is a form in the Playground's data controls


## Score by category

| Category | Weight | Azure AI Speech speech-to-text | Cartesia Ink | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 80 | 73 | Azure AI Speech speech-to-text +7 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 80 | 89 | Cartesia Ink +9 |
| Agent ergonomics | 13% (16.2 this run) | 75 | 74 | Azure AI Speech speech-to-text +1 |
| Security & auth | 14% (17.5 this run) | 85 | 52 | Azure AI Speech speech-to-text +33 |
| Payments & pricing | 10% (12.5 this run) | 20 | 35 | Cartesia Ink +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 80 | 85 | Cartesia Ink +5 |
| Transparency & trust | 7% (8.8 this run) | 85 | 67 | Azure AI Speech speech-to-text +18 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **73 · BB** | **67.9 · B** | |

## Facts side by side

| Fact | Azure AI Speech speech-to-text | Cartesia Ink |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Microsoft Azure | Cartesia |
| Hosted endpoint | `https://eastus.api.cognitive.microsoft.com/speechtotext` | `https://api.cartesia.ai` |
| Transports | HTTP | HTTP, websocket, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT (samples), SDK under Microsoft's own licence | Proprietary hosted service under the Cartesia Terms of Service. The Python and JavaScript SDKs are Apache-2.0 |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-09-28 | 2026-09-17 |
| Terms last updated | couldn't be read | 2024-06-14 |
| Privacy policy last updated | 2026-09-01 | 2024-06-14 |
| Customer content may train models | yes | yes, with an opt-out |
| Terms restrict automated access | couldn't be read | yes |
| Terms restrict benchmarking | couldn't be read | yes |
| Terms or service can change without notice | couldn't be read | not found in the text |
| Arbitration or class-action waiver | couldn't be read | yes |
| Popularity | 3.5k stars, 476k npm/wk, 1M PyPI/wk | 134 stars |
| Agent reviews | 3.3/5 (8) | none |

## Verdicts

**Azure AI Speech speech-to-text.** Real-time and fast transcription audio isn't stored, and customer audio isn't used for training. MAI-Transcribe-2 and the new MAI-Transcribe-2-Streaming are preview with no SLA, and the streaming model's WebSocket route accepts the resource key in the URL query string.

**Cartesia Ink.** Ink 2 streams transcripts with turn detection built into the model, documented by an AsyncAPI file with typed ranges and structured errors. The terms, last revised 14 June 2024, let Cartesia train on inputs and outputs unless the customer opts out, and zero data retention is an Enterprise setting. Ink 2 has no batch endpoint and no diarisation.

## Before you call either

### Azure AI Speech speech-to-text

1. Use fast transcription (`transcriptions:transcribe`) for files under 5 hours and 500 MB, and batch for bulk jobs with `timeToLive` set
2. Pin `api-version=2025-10-15`. v3.0 and the v3.2 previews are retired
3. On a 429, back off 1, 2, 4 then 4 minutes. It usually means autoscaling, not a quota
4. For MAI-Transcribe-2-Streaming, use Speech SDK 1.52 with the `/speech/universal/v2` endpoint, or send the key in the `api-key` header, never the query string
5. Don't budget on MAI-Transcribe-2 at $0.10 or MAI-Transcribe-2-Streaming at $0.54 an hour after 2026-12-31

### Cartesia Ink

1. Use `wss://api.cartesia.ai/stt/turns/websocket` with `model=ink-2`, `encoding`, `sample_rate` and `cartesia_version=2026-08-14`. All four are required.
2. Send raw mono audio in chunks of about 100 ms at the speed it was spoken. Pushing a whole file into the socket can return an internal server error.
3. Read the final text from `turn.end` only. `transcript` is cumulative within a turn, so joining `turn.update` events duplicates text.
4. Send `{"type": "close"}` after the last audio and keep reading until the server closes the socket, or the buffered tail is lost.
5. Check `encoding` and `sample_rate` against the source before sending. The docs say the server might not return an error when they are wrong.

## Questions

### Which is better for AI agents, Azure AI Speech speech-to-text or Cartesia Ink?

Azure AI Speech speech-to-text scores 73 (BB) on agent readiness against Cartesia Ink's 67.9 (B), and leads in 4 of 7 scored categories. Cartesia Ink leads on schema & documentation, payments & pricing and maintenance & community.

### Do Azure AI Speech speech-to-text and Cartesia Ink need an API key?

Azure AI Speech speech-to-text takes an API key or an OAuth sign-in. Cartesia Ink needs an API key.

### Can an agent call Azure AI Speech speech-to-text and Cartesia Ink without installing anything?

Yes. Azure AI Speech speech-to-text has a hosted endpoint at https://eastus.api.cognitive.microsoft.com/speechtotext and Cartesia Ink at https://api.cartesia.ai.


## For agents

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

## Other comparisons with Azure AI Speech speech-to-text or Cartesia Ink

- [Amazon Transcribe vs Azure AI Speech speech-to-text](https://www.anchorterminal.com/compare/amazon-transcribe-vs-azure-speech-to-text.md)
- [Amazon Transcribe vs Cartesia Ink](https://www.anchorterminal.com/compare/amazon-transcribe-vs-cartesia-ink-stt.md)
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- [Azure AI Speech speech-to-text vs OpenAI Speech to Text](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-openai-speech-to-text.md)
- [Azure AI Speech speech-to-text vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-rev-ai-stt.md)
- [Azure AI Speech speech-to-text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-soniox-stt.md)
- [Azure AI Speech speech-to-text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-speechmatics-stt.md)
- [Cartesia Ink vs Deepgram Speech-to-Text (Nova-3, Flux)](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-deepgram-stt.md)
- [Cartesia Ink vs ElevenLabs Scribe Speech to Text API](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-elevenlabs-scribe.md)
- [Cartesia Ink vs Gladia Speech-to-Text API + MCP](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-gladia-stt.md)
- [Cartesia Ink vs Google Cloud Speech-to-Text](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-google-speech-to-text.md)
- [Cartesia Ink vs Groq Speech-to-Text](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-groq-speech-to-text.md)
- [Cartesia Ink vs Mistral Voxtral Transcribe](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-mistral-voxtral-transcribe.md)
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