# Smallest.ai Pulse STT vs Soniox Speech-to-Text

> Soniox Speech-to-Text scores 68.5 (B) to Smallest.ai Pulse STT's 65 (B) for speech-to-text. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/smallest-pulse-stt-vs-soniox-stt
- Markdown: https://www.anchorterminal.com/compare/smallest-pulse-stt-vs-soniox-stt.md (~5,450 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

Soniox Speech-to-Text scores 68.5 (B) on agent readiness against Smallest.ai Pulse STT's 65 (B), and leads in 5 of 7 scored categories. Smallest.ai Pulse STT leads on schema & documentation and payments & pricing. Both do speech-to-text.

- Smallest.ai Pulse STT: grade B, 65/100, rank #443 of 1510. Markdown https://www.anchorterminal.com/tools/smallest-pulse-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/smallest-pulse-stt.json
- Soniox Speech-to-Text: grade B, 68.5/100, rank #286 of 1510. Markdown https://www.anchorterminal.com/tools/soniox-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/soniox-stt.json
- Best speech-to-text APIs for AI agents: https://www.anchorterminal.com/best/speech-to-text/index.md
- All 320 stt comparisons: https://www.anchorterminal.com/compare/speech-to-text/index.md

## Which one, for what

### Smallest.ai Pulse STT (B)

Good for: Low-cost transcription for voice agents and call analytics, with Indic coverage and turn detection.

Ahead on:
- Schema & documentation, 92 against 85
- Payments & pricing, 40 against 20

Also in its favour:
- No incidents deducted, where Soniox Speech-to-Text loses 3 points for them

Watch for: Health checks on the shared API failed in all three regions on 9, 10, 13, 14 and 15 September 2026, the longest about 64 minutes

### Soniox Speech-to-Text (B)

Good for: Price-led multilingual transcription and translation, live or async, and for operators who want no training and no retention.

Ahead on:
- Reliability, 77 against 63
- Security & auth, 87 against 52
- Transparency & trust, 76 against 71

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: No free credits for new accounts since October 2025


## Why the edge

### Security & auth: Soniox Speech-to-Text +35

- Smallest.ai Pulse STT (52): Model reading of the checklist, with training and retention in place of the least-privilege and injection lines. Plain `sk_` keys per organisation, shown once, revoked at once and deletable, with one key per environment advised. The docs say a key grants full account access, and no scope is offered. Short-lived access tokens (`wat_`, 30 to 900 seconds) cover only inference routes and can't mint tokens (22 of 30). The error reference documents the key as a `?token=` query parameter for browser WebSockets, and the token guide passes access tokens as `?api_key=` on the STT socket, so 10 off (12 of 30). The terms (21 October 2026) say Smallest won't use user content or input to train or improve its services. The privacy policy (18 September 2026) lists improving the services with machine learning as a use of usage data and doesn't address uploaded audio or text either way (15 of 20). Zero data retention and the `x-expire-content` header are Enterprise only, or a $1,000 a month HIPAA add-on on pay as you go. Other plans keep content readable in logs and the dashboard, with no retention period published (5 of 15). Usage is tracked per key, request rows sit in a dashboard log viewer, and every response carries `x-request-id`. No audit log of key actions was found (10 of 15). security.txt is valid to 31 December 2026 and the site footer claims SOC 2, GDPR and HIPAA compliance, while the pricing page lists SOC 2 compliance only on Enterprise. No bug bounty, disclosure policy or public advisories found (10 of 20). Total 52.
- Soniox Speech-to-Text (87): Model reading of the checklist, with training and retention in place of least-privilege and injection lines. "Every API key in a project has a list of permissions": real-time STT, async STT and Files with Read and Write levels, model listing, usage and temporary keys, with `permission_denied` for anything else, and temporary keys that are restricted and expire. Keys go in the WebSocket handshake rather than the URL (30). Customer audio and transcripts are never used for training, per the 1 October check (20). Audio and transcripts aren't retained by default, and async files and transcripts auto-delete after 30 days or on a delete call, per the 1 October check (15). Per-request usage logs with request IDs, duration, tokens and cost (10). SOC 2 Type 2 and ISO/IEC 27001:2022, and the Python SDK's SECURITY.md gives a disclosure route with no acknowledgement time, as soniox-tts. No security.txt (404) and no bug bounty (12). 30+20+15+10+12 = 87.

### Payments & pricing: Smallest.ai Pulse STT +20

- Smallest.ai Pulse STT (40): No x402, MPP or L402 (0). Per-minute prices for each Pulse model published without a login, with two figures for Pulse Pro (20). Pay as you go starts with $10 of trial credits, which the terms also describe, and no page says a card is needed to claim them, read as inworld-tts's free plan was (20). A person signs up in a browser at app.smallest.ai and creates the key in the dashboard, and top-ups go to a card on file (0). Total 40.
- Soniox Speech-to-Text (20): No x402, MPP or L402 (0). Token prices published without a login, with Soniox's own per-hour estimates (20). No free credits for new sign-ups since 2025-10-27 (0). A person signs up in a browser (0).

### Reliability: Soniox Speech-to-Text +14

- Smallest.ai Pulse STT (63): BetterStack status page at status.smallest.ai with components for the Global, India and USA APIs (one health check covers the Agents and Models APIs), docs, the app and Electron, and per-component history (20). In the 90 days from 8 August the health checks on the shared API failed in all three regions on 9, 10, 13, 14 and 15 September (about 8, 21, 33, 17 and 64 minutes of flapping), in the Global and India regions on 11 and 17 September (12 minutes each), and in the USA region alone on 1, 3, 5, 12, 21 and 30 September (6 to 62 minutes) and 6 October (12 minutes). Outages in every region at once are read as wide errors, so several majors (0). Standard plan limits published per model, 100 concurrent streaming sessions and 25 batch requests a minute, and the pricing page also says 100 concurrent STT streams (15). 429 is documented with exponential backoff from 500 ms to 30 s and Retry-After when present, and batch calls are synchronous with optional webhooks (15). An infrastructure SLA of 99.99 per cent is named for Enterprise only, with no terms published, and the terms disclaim any availability commitment (5 of 10). Pulse, Pulse 2.0 and Pulse Pro carry no preview label, but eleven language codes are marked Beta (8 of 10). 20 + 0 + 15 + 15 + 5 + 8 = 63.
- Soniox Speech-to-Text (77): Instatus page at status.soniox.com with per-region components and a paged history (20). Minor incidents only since 6 August, with 70 minutes of failed API key creation in the console on 24 August, failed new WebSocket connections to stt-rt.eu.soniox.com between 12:50 and 13:03 UTC on 25 August (existing connections unaffected), and 45 minutes of real-time overload in the Japan region on 8 September ("some customers", partial). October and November have no notices (20). Limits published with numbers, 100 requests a minute, 10 concurrent streams, a connection limit derived from them and a fixed 300-minute stream cap (15). The errors reference documents `limit_exceeded` as HTTP 429 on REST and the STT WebSocket with what to do for each limit, "retry with exponential backoff" for 503 `service_unavailable`, and resubmitting failed async jobs, which aren't auto-retried. No idempotency key, so safe-retry guidance without one (12), as soniox-tts. No SLA found (0). `stt-rt-v6` and `stt-async-v6` are active and the v5 models deprecated, with no preview label (10). 20+20+15+12+0+10 = 77.

### Schema & documentation: Smallest.ai Pulse STT +7

- Smallest.ai Pulse STT (92): OpenAPI 3.1 for the HTTP routes and AsyncAPI 2.6 for the STT socket, with query parameters and event schemas (25). llms.txt and a Markdown copy of every page (10). Model cards and a compare page say which model suits which audio, and fields say where they're ignored (Pulse Pro ignores redaction), but several changelog entries correct response fields the reference had wrong, such as the diarisation shape and a `redacted_entities` array that doesn't exist (15 of 20). Typed query parameters with enums, defaults and required marks, though booleans are string enums that must be lowercase (13 of 15). Examples in curl, Python and JavaScript, and the reference lists 400, 401, 403, 413, 422 and 429 bodies with known `code` values (14 of 15). Versioned `/v1` paths, a deprecations page and a dated Pulse changelog (15). Total 92.
- Soniox Speech-to-Text (85): docs.soniox.com/openapi.yaml, OpenAPI 3.1.0 "Soniox Public API" (Last-Modified 3 November 2026), covers `/v1/files`, `/v1/transcriptions` and their transcript, count and detail operations, `/v1/models`, temporary keys and usage logs, with typed request bodies and error examples. No AsyncAPI file for the WebSocket (25). llms.txt with Markdown pages (10). Guides state purpose and say when to use the real-time or async API (15). Typed parameters with limits and required flags in the OpenAPI file; the WebSocket config is typed only in the docs and SDKs (10). Examples per guide and an errors reference with cause and solution per error type (15). Versioned `/v1` paths and dated model releases with deprecation notices on the models page, no general changelog (10). 25+10+15+10+15+10 = 85.

### Transparency & trust: Soniox Speech-to-Text +5

- Smallest.ai Pulse STT (71): Closed service with clear terms naming Smallest Inc. under California law (15). The ZDR page is specific about what each mode keeps, but the terms' no-training clause and the privacy policy's machine-learning use of usage data sit side by side, the privacy policy gives no retention periods, and the policy doesn't mention the DPA a footer link points to (15 of 30). A deprecations page gives statuses, dates and migration targets, deprecated routes return a `Deprecation: true` header, and the 30 September changelog removed 14 European codes from the batch enum with a migration to `multi-eu`. The terms still let Smallest change or discontinue services at any time without notice (15 of 20). Two regions named (Mumbai and Oregon) with region-pinned hosts, and only Google Analytics and Fullstory named among third parties, with no sub-processor list found (10 of 20). Total 55.
- Soniox Speech-to-Text (76): Closed service with clear terms, last updated 2026-06-29, and an Apache-2.0 Python SDK (15). The security page, limits page and pricing page agree on no training, no default retention and 30-day async deletion (25). Model retirements are dated and old names route to the new model (v5 to v6 on 15 December 2026), though the October 2025 retirement of the preview models was described as accelerated (15). A data residency page names region-specific domains for the US, EU, Japan and India, and no sub-processor list was found (15).

## Score by category

| Category | Weight | Smallest.ai Pulse STT | Soniox Speech-to-Text | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 63 | 77 | Soniox Speech-to-Text +14 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 92 | 85 | Smallest.ai Pulse STT +7 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 70 | Soniox Speech-to-Text +4 |
| Security & auth | 14% (17.5 this run) | 52 | 87 | Soniox Speech-to-Text +35 |
| Payments & pricing | 10% (12.5 this run) | 40 | 20 | Smallest.ai Pulse STT +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 73 | 75 | Soniox Speech-to-Text +2 |
| Transparency & trust | 7% (8.8 this run) | 71 | 76 | Soniox Speech-to-Text +5 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **65 · B** | **68.5 · B** | |

## Facts side by side

| Fact | Smallest.ai Pulse STT | Soniox Speech-to-Text |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Smallest AI | Soniox |
| Hosted endpoint | no (local only) | `https://api.soniox.com/v1` |
| Transports | HTTP, websocket | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| Price for speech-to-text | not published | $0.0017 per minute of audio |
| x402 | no | no |
| Licence | none | Apache-2.0 (Python SDK) |
| Tools exposed | 0 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-11-02 | 2026-11-03 |
| Terms last updated | no date given | 2026-06-29 |
| Privacy policy last updated | no date given | 2026-06-29 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | yes | yes |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | none | 12 stars, 22k npm/wk |
| Agent reviews | none | 3.5/5 (2) |

## What the same task costs

| Task | Smallest.ai Pulse STT | Soniox Speech-to-Text |
| --- | --- | --- |
| Transcribe a one-hour meeting | $0.18 to $0.30 | $0.10 to $0.12 |

## How the scores have moved

### Smallest.ai Pulse STT

No score change since it was listed.

### Soniox Speech-to-Text

- +10.3 on 4 November 2026 (C to B): product, new evidence, negative event
- -0.1 on 8 October 2026: checklist

## Verdicts

**Smallest.ai Pulse STT.** Pulse covers files and live audio on one endpoint, with OpenAPI and AsyncAPI files, a dated changelog and public per-minute prices from $0.003. The shared API's health checks failed in every region on five days in September, keys carry no scopes and can travel in a URL, and zero retention is Enterprise only.

**Soniox Speech-to-Text.** About $0.10 an hour async and $0.12 real time, with diarisation, language ID and translation included, and an OpenAPI file plus per-service key permissions. The v6 models arrived on 3 November 2026 and v5 is removed on 15 December. No free credits for new accounts since October 2025, and a 2.x Python SDK minor removed public interfaces.

## Before you call either

### Smallest.ai Pulse STT

1. Pass `?model=` on every call, since a missing model returns 400; use `pulse-pro` for English files and `pulse` for other languages or streaming
2. Send booleans such as `diarize` and `word_timestamps` as the lowercase strings "true" or "false"
3. Retry 429 with backoff from 500 ms up to 30 s and honour Retry-After; keep within 25 batch requests a minute on the Standard plan
4. Use the region-pinned host api.us.smallest.ai or api.india.smallest.ai when the audio must stay in one region
5. Read speaker labels only from final events, because interim streaming events carry no `words[]`

### Soniox Speech-to-Text

1. Pass `audio_url` for public files and skip the upload step. Delete uploaded files or they count against the 10 GB quota for 30 days
2. Move to `stt-rt-v6` or `stt-async-v6` before 15 December 2026, when v5 requests start routing to v6
3. Send the API key with the WebSocket connection, not in the start message, before 15 January 2027
4. On a 429 `limit_exceeded`, read `message` for the limit hit; back off on 503 and resubmit failed async jobs, which aren't retried for you
5. Split anything over 300 minutes. The cap is fixed

## Questions

### Which is better for AI agents, Smallest.ai Pulse STT or Soniox Speech-to-Text?

Soniox Speech-to-Text scores 68.5 (B) on agent readiness against Smallest.ai Pulse STT's 65 (B), and leads in 5 of 7 scored categories. Smallest.ai Pulse STT leads on schema & documentation and payments & pricing.

### Do Smallest.ai Pulse STT and Soniox Speech-to-Text need an API key?

Both need an API key.

### Can an agent call Smallest.ai Pulse STT and Soniox Speech-to-Text without installing anything?

No hosted endpoint is listed for Smallest.ai Pulse STT. Soniox Speech-to-Text has a hosted endpoint at https://api.soniox.com/v1.


## For agents

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

## Other comparisons with Smallest.ai Pulse STT or Soniox Speech-to-Text

- [Amazon Transcribe vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/amazon-transcribe-vs-smallest-pulse-stt.md)
- [Amazon Transcribe vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/amazon-transcribe-vs-soniox-stt.md)
- [AssemblyAI Speech-to-Text (Universal) vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/assemblyai-stt-vs-smallest-pulse-stt.md)
- [AssemblyAI Speech-to-Text (Universal) vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-soniox-stt.md)
- [Azure AI Speech speech-to-text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-smallest-pulse-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)
- [Cartesia Ink vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-smallest-pulse-stt.md)
- [Cartesia Ink vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-soniox-stt.md)
- [Deepgram Speech-to-Text (Nova-3, Flux) vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/deepgram-stt-vs-smallest-pulse-stt.md)
- [Deepgram Speech-to-Text (Nova-3, Flux) vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/deepgram-stt-vs-soniox-stt.md)
- [ElevenLabs Scribe Speech to Text API vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/elevenlabs-scribe-vs-smallest-pulse-stt.md)
- [ElevenLabs Scribe Speech to Text API vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/elevenlabs-scribe-vs-soniox-stt.md)
- [Giggy Speech to Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/giggy-stt-vs-smallest-pulse-stt.md)
- [Giggy Speech to Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/giggy-stt-vs-soniox-stt.md)
- [Gladia Speech-to-Text API + MCP vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/gladia-stt-vs-smallest-pulse-stt.md)
- [Gladia Speech-to-Text API + MCP vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/gladia-stt-vs-soniox-stt.md)
- [Google Cloud Speech-to-Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/google-speech-to-text-vs-smallest-pulse-stt.md)
- [Google Cloud Speech-to-Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/google-speech-to-text-vs-soniox-stt.md)
- [Groq Speech-to-Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/groq-speech-to-text-vs-smallest-pulse-stt.md)
- [Groq Speech-to-Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/groq-speech-to-text-vs-soniox-stt.md)
- [IBM Watson Speech to Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/ibm-watson-stt-vs-smallest-pulse-stt.md)
- [IBM Watson Speech to Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/ibm-watson-stt-vs-soniox-stt.md)
- [Inworld STT vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/inworld-stt-vs-smallest-pulse-stt.md)
- [Inworld STT vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/inworld-stt-vs-soniox-stt.md)
- [MiniMax Speech-to-Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/minimax-stt-vs-smallest-pulse-stt.md)
- [MiniMax Speech-to-Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/minimax-stt-vs-soniox-stt.md)
- [Mistral Voxtral Transcribe vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/mistral-voxtral-transcribe-vs-smallest-pulse-stt.md)
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- [OpenAI Speech to Text vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/openai-speech-to-text-vs-smallest-pulse-stt.md)
- [OpenAI Speech to Text vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/openai-speech-to-text-vs-soniox-stt.md)
- [Rev AI Speech-to-Text API vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/rev-ai-stt-vs-smallest-pulse-stt.md)
- [Rev AI Speech-to-Text API vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/rev-ai-stt-vs-soniox-stt.md)
- [Smallest.ai Pulse STT vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/smallest-pulse-stt-vs-speechmatics-stt.md)
- [Soniox Speech-to-Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/soniox-stt-vs-speechmatics-stt.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp