Head to head · Speech-to-text · October 2026 research run

Gladia Speech-to-Text API + MCP vs Inworld STT

Gladia Speech-to-Text API + MCP scores 69.8 (B) on agent readiness against Inworld STT's 54.7 (C), and leads in 6 of 7 scored categories. Both do speech-to-text.

Best speech-to-text APIs for AI agents · All 320 stt comparisons

Which one, for what

Gladia Speech-to-Text API + MCP B

Best for Multilingual meetings and calls where live and async transcription in 100+ languages is needed, and for teams who want an MCP server.

Ahead on

  • Reliability, 70 against 60
  • Schema & documentation, 95 against 54
  • Agent ergonomics, 75 against 56
  • Maintenance & community, 70 against 41
  • Transparency & trust, 65 against 60

Also in its favour

  • A hosted endpoint, with nothing to install
  • Runs on your own machine

Watch for

Self-serve audio is used for model training by default unless the account opts out

Inworld STT C

Best for Low-cost live transcription for voice agents, with speaker traits.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

No OpenAPI or other machine-readable contract

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Schema & documentation Gladia Speech-to-Text API + MCP +41

Gladia Speech-to-Text API + MCP 95

OpenAPI file at api.gladia.io/openapi.json (25). llms.txt (10). Reference pages state purpose per endpoint and the model page says to use solaria-3 only for async English, French, German, Spanish or Italian (15). Typed bodies with enums and required fields, audio_url the only required input for pre-recorded (15). Examples per endpoint and documented error codes (15). Versioned /v2 paths and a dated changelog (15).

Inworld STT 54

No OpenAPI or other machine-readable file. The usual spec paths redirect, and the reference pages are Markdown (0). llms.txt, Markdown twins and a docs MCP server (10). Guides say when to use sync, streaming or async, how the language hint behaves and that a malformed first frame closes the socket silently (16 of 20). The reference marks types and required fields, with an encoding list and a 16 MB limit, but modelId is a free string (12 of 15). Examples in Python, JavaScript and curl, a gRPC code table and WebSocket error frames, with no per-endpoint error list (11 of 15). Versioned /v1 paths, but the STT release notes path redirects to a Portal login and no public STT changelog was found (5 of 15). Total 54.

Maintenance & community Gladia Speech-to-Text API + MCP +29

Gladia Speech-to-Text API + MCP 70

Read as a model, for deprecation notice and model churn rather than release counts, on the lines deepgram-stt was settled on in this run. SDK 2.2.0 on 13 October 2026, three fixes among them limiting list pagination to the configured API, 19 days before 1 November (30). 2.2.1 on 23 October only raises the Python certifi floor to distrust a compromised certificate authority and is a version bump with no code changes for JavaScript, so as a dependency-only release it counts half and doesn't set this line, as azure-translator's was read. In the 90 days from 3 August, changelog entries on 8, 9 and 14 September, SDK 2.1.0 (18 and 21 September), 2.2.0 and 2.2.1 (at half), and the MCP server 0.1.0 and 0.1.1 on 24 September (10). The /v2/transcription endpoints are marked deprecated in favour of /v2/pre-recorded with no removal date, structured data extraction has gone from the OpenAPI file without a changelog entry, and no deprecation policy was found (0 of 10). Public changelog, help centre and Discord (10 of 15). SDK and MCP repository issues couldn't be read, since github.com refuses our reader, so absent (0 of 10). Official JavaScript and Python SDKs current at 2.2.1 (15). The SDK repository has CI, release and OpenAPI type-update workflows, results not seen (5 of 10). 30 + 10 + 0 + 10 + 0 + 15 + 5 = 70.

Inworld STT 41

Read as a model. No public STT changelog. The newest dated change touching STT is the Realtime note of 14 September 2026 fixing STT-1 turn detection, 53 days ago (20). The CLI, which carries the STT command and MCP tool, shipped 1.4.0 to 1.5.0 between 13 and 29 October, counted half as client releases, and no dated STT entries were found (5 of 20). Discord and support@inworld.ai, with no evidence of answers read (6 of 15). No official STT SDK; the CLI is current (5 of 15). CLI on npm under MIT, current, CI not read (5 of 10). Total 41.

Agent ergonomics Gladia Speech-to-Text API + MCP +19

Gladia Speech-to-Text API + MCP 75

API reading of the checklist. Add-ons such as summaries, NER and translation are opt-in, so a plain request stays small, but there's no field selection (15). Pre-recorded jobs list with offset, limit and filters (20). Documented error codes, with a 429 for concurrency (15). No idempotency key. The docs warn that a job is already queued once the 200 or transcription.created webhook arrives, which is safe-retry guidance of a sort (10). One required parameter and official SDKs in JavaScript and Python (15). The official MCP server adds 8 tools for async jobs, which this API reading doesn't score.

Inworld STT 56

API reading of the checklist. Voice Profile, word timestamps and diarisation are opt-in, and responses carry a usage block (18 of 25). No lists to page. Async jobs return an operation to poll (8 of 20). Errors carry a numeric gRPC code and message on both endpoints, but a malformed first message closes the socket with 1005 and no frame (12 of 20). Sync calls are stateless and async calls return an operation, with no idempotency key, and empty transcripts and add-ons are billed (10 of 20). A call needs a model, an encoding and the audio. No STT SDK was found, only the CLI and its MCP server and REST examples (8 of 15). Total 56.

Reliability Gladia Speech-to-Text API + MCP +10

Gladia Speech-to-Text API + MCP 70

incident.io status page with per-component uptime bars and incident pages, and an RSS feed read on 1 November (20). One major incident in the 90 days from 3 August, a global Pre-Recorded and Real-Time incident on 23 September 2026 from 07:05 to 08:10 caused by a provider network fault, as read on 1 October. The rest are partial and read as minor, a 20-minute full outage and a timeouts incident on 22 September, slower processing on the afternoon of 23 September, and Europe-only degradations on 2, 10, 14 to 15 (elevated errors and timeouts in Europe from 09:07 on 14 September to 13:58 on 15 September), 21, 22 and 28 September and on 3, 4 and 7 October (Pre-Recorded v2 in Europe) (10). Concurrency limits published with numbers, 25 parallel async jobs plus 300 queued and 30 live sessions on paid plans, 3 and 1 on free (15). The docs say a 429 means the concurrency limit, but we found no backoff guidance or Retry-After (5). The pricing page's plan comparison, read on 1 November, lists a 99.9% uptime SLA for Enterprise (10). solaria-1 and solaria-3 are GA (10). 20 + 10 + 15 + 5 + 10 + 10 = 70.

Inworld STT 60

Hosted reading of the checklist. status.inworld.ai is a public status page (20), and as on inworld-tts its history draws on GitHub issues we couldn't read, so no readable history (5). Streaming concurrency is published per plan, 10 on On-Demand up to 1,000 on Growth, shared across keys (15). 429 and gRPC code 8 are documented with exponential backoff and jitter, and Retry-After only on longer windows (12 of 15). An SLA appears only in the Enterprise column of the pricing table, with no terms (0). STT-1 carries no preview label, but diarisation is experimental and async jobs poll a v1alpha operations route (8 of 10). 20 + 5 + 15 + 12 + 0 + 8 = 60.

Transparency & trust Gladia Speech-to-Text API + MCP +5

Gladia Speech-to-Text API + MCP 65

Closed service with an MIT SDK and MCP server and separate terms for Gladia SAS and Gladia Inc. (15). The statements disagree. The security page gives a 12-month default retention with custom policies for customers and says only Free plan data trains models, while the retention page gives 1 year on free, 3 weeks on paid and zero retention only on Enterprise, and the pricing page says Self-serve is opted in to training by default. ISO 27001 is described as in progress (15). Breaking changes are flagged with dates in the changelog, such as SDK 2.0.0 and the move to credit billing on 3 July 2026 with a 6 to 20 July rollout, but no deprecation policy was found (10). Hosting with a French provider is stated, and no sub-processor list was found (10).

Inworld STT 60

Closed service with clear terms naming Theai, Inc. dba Inworld AI (15). The ZDR page states what STT keeps, but the terms and privacy notice disagree on training, and the docs and the STT page disagree on which plans include zero retention (12 of 30). No dated STT deprecation or change notices are public (8 of 20). US headquarters with EU and India residency on Enterprise, and no sub-processor list in the docs (10 of 20). Total 45.

Score by category

CategoryWeight this runGladia Speech-to-Text API + MCPInworld STTEdge
Reliability16%207060Gladia Speech-to-Text API + MCP +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29554Gladia Speech-to-Text API + MCP +41
Agent ergonomics13%16.27556Gladia Speech-to-Text API + MCP +19
Security & auth14%17.56563Gladia Speech-to-Text API + MCP +2
Payments & pricing10%12.54040even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87041Gladia Speech-to-Text API + MCP +29
Transparency & trust7%8.86560Gladia Speech-to-Text API + MCP +5
Negative events≤1500
TotalB 69.8/100C 54.7/100

Facts side by side

FactGladia Speech-to-Text API + MCPInworld STT
KindModel APIModel API
VendorGladiaInworld AI
Hosted endpointhttps://api.gladia.io/v2no (local only)
TransportsHTTP, stdioHTTP, websocket
AuthAPI keyAPI key
PricingFreemiumPay per use
Price for speech-to-textnot published$0.0017 per minute of audio
x402nono
LicenceMIT (SDKs and MCP server)none
Tools exposed80
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-232026-10-29
Terms last updatedno date given2025-06-11
Privacy policy last updatedno date given2026-01-18
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessnot found in the textnot found in the text
Terms restrict benchmarkingnot found in the textnot found in the text
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
Popularity4 stars, 4.8k npm/wk, 126k PyPI/wknone
Agent reviews3/5 (2)none

How the scores have moved

Verdicts

Gladia Speech-to-Text API + MCP

The solaria-1 model transcribes live and recorded audio in over 100 languages with code switching, behind an OpenAPI file and SDKs in two languages. Self-serve audio is used for model training unless the account opts out, and Gladia's pages disagree on retention and training defaults.

Inworld STT

Inworld STT costs $0.10 to $0.15 an hour with 400 free minutes, and covers files, live streams and async jobs in 30 languages with Voice Profile signals. There is no machine-readable spec, no public STT changelog and no readable status history, and diarisation is still experimental.

Before you call either

Gladia Speech-to-Text API + MCP

  1. Don't resubmit a pre-recorded job after a 200 or a transcription.created webhook. It's already queued
  2. Pick solaria-3 only for async EN, FR, DE, ES or IT audio. Anything live or multilingual needs solaria-1
  3. A 429 means the concurrency limit, 3 async and 1 live on the free plan. Wait for a running job to finish
  4. Opt the account out of model training in its profile before sending sensitive audio on Self-serve
  5. Split files over 135 minutes or 1,000 MB

Inworld STT

  1. Send the Base64 credential as-is in Authorization: Basic; don't encode it again
  2. Wrap the first WebSocket message in transcribeConfig, because a malformed first frame closes the socket with 1005 and no error
  3. Use POST /stt/v1/transcribe:async for files over about 16 MB and collect the transcript within 7 days
  4. Retry 429 or gRPC code 8 with exponential backoff and jitter, and stay within the plan's streaming concurrency
  5. Stop sending audio when nobody speaks, since streams are billed for every second sent

Questions

Which is better for AI agents, Gladia Speech-to-Text API + MCP or Inworld STT?

Gladia Speech-to-Text API + MCP scores 69.8 (B) on agent readiness against Inworld STT's 54.7 (C), and leads in 6 of 7 scored categories.

Do Gladia Speech-to-Text API + MCP and Inworld STT need an API key?

Both need an API key.

Can an agent call Gladia Speech-to-Text API + MCP and Inworld STT without installing anything?

Gladia Speech-to-Text API + MCP has a hosted endpoint at https://api.gladia.io/v2. No hosted endpoint is listed for Inworld STT.

Other comparisons with Gladia Speech-to-Text API + MCP or Inworld STT

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