{
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      "name": "AssemblyAI Speech-to-Text (Universal)",
      "vendor": "AssemblyAI",
      "vendorUrl": "https://www.assemblyai.com",
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      "category": "speech-to-text",
      "summary": "Speech-to-text APIs for recorded audio and live streams, with speaker identification, translation and redaction options.",
      "url": "https://www.anchorterminal.com/tools/assemblyai-stt",
      "markdownUrl": "https://www.anchorterminal.com/tools/assemblyai-stt.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/assemblyai-stt.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/assemblyai-stt.json",
      "repo": "https://github.com/AssemblyAI/assemblyai-python-sdk",
      "license": "MIT (SDKs)",
      "transports": [
        "http",
        "streamable-http"
      ],
      "remoteUrl": "https://api.assemblyai.com/v2",
      "packages": [
        {
          "registry": "npm",
          "name": "assemblyai"
        },
        {
          "registry": "pypi",
          "name": "assemblyai"
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      ],
      "auth": "api-key",
      "authNotes": "API key in the `authorization` header. Temporary tokens for browser streaming. The docs MCP needs no key.",
      "pricing": "usage",
      "pricingNotes": "Free tier with no card covers up to 185 hours of pre-recorded or 333 hours of streaming. Then pay as you go per hour of audio. Universal-3.5 Pro $0.21, Universal-2 $0.15, Universal-3.6 Pro Realtime $0.45, Universal-Streaming $0.15, Sync $0.45. Diarisation $0.02 an hour on files and $0.12 on streams, keyterms $0.05 on Universal-3.5 Pro, translation $0.06. Streaming bills session time, not audio sent (https://www.assemblyai.com/pricing).",
      "priceSummary": "Pay per use",
      "where": "hosted",
      "x402": {
        "level": "no",
        "evidence": "No x402 or machine payment in the docs or pricing. Card or prepaid credits only (checked 2026-09-30).",
        "endpoints": []
      },
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      "llmsTxt": "https://www.assemblyai.com/docs/llms.txt",
      "openapi": "https://www.assemblyai.com/docs/openapi.yaml",
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        "speech.stt",
        "speech.streaming",
        "speech.batch",
        "speech.diarisation",
        "speech.languages",
        "speech.translation"
      ],
      "tags": [
        "hosted",
        "no-card",
        "free-tier",
        "closed-source",
        "python",
        "typescript",
        "openapi",
        "llms-txt",
        "mcp",
        "streaming",
        "batch",
        "webhooks",
        "async-jobs",
        "enterprise"
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      "graded": true,
      "anchor": {
        "graded": true,
        "score": 67,
        "grade": "B",
        "agentReady": false,
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        "ranked": true,
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        "categoryRank": 8,
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          "maintenance": 80,
          "payments": 40,
          "reliability": 70,
          "schema": 95,
          "security": 50,
          "transparency": 78
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          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-01"
        },
        "negative": -3,
        "negativeNotes": [
          "2026-07-10, the async `speech_model` parameter began returning 400 for current model names and silently routing legacy names to the default model, and `universal-3-pro` was blocked for new accounts and accounts inactive for 7 days, all announced in the changelog the same day. We found no earlier notice (https://www.assemblyai.com/changelog). Documented, so the minimum deduction."
        ],
        "verdict": "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.",
        "strengths": [
          "OpenAPI 3.1 file with typed inputs and error responses on every operation",
          "Universal-2 covers 99 languages at $0.15 an hour, Universal-3.5 Pro is $0.21",
          "Transcript lists paginate with `limit`, `before_id` and `after_id`, and transcripts come back as sentences, paragraphs, SRT or VTT",
          "Free tier with no card, up to 185 hours pre-recorded",
          "TTL deletion from 1 hour and a delete endpoint for transcripts"
        ],
        "weaknesses": [
          "Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026",
          "Free accounts can't opt out of model training",
          "The HTTP rate limit returns 403 with no Retry-After",
          "Streaming bills the time the socket is open, up to a 3-hour auto-close",
          "No security.txt or published disclosure policy"
        ],
        "agentNotes": [
          "Send `{\"type\":\"Terminate\"}` to close every stream, or billing runs to the 3-hour auto-close",
          "Use `speech_models` (plural). The singular `speech_model` now returns 400 for current model names",
          "Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks",
          "Fetch `/sentences` or `/paragraphs` instead of the full transcript when you only need text",
          "Opt out in Data Controls on a paid account before sending customer audio"
        ],
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          "kind": "remote",
          "measured": false
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        "avgRating": 3.5,
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          "reliability": 70,
          "schema": 95,
          "security": 50,
          "transparency": 70
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        "provenanceScore": 86
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      "connect": {
        "http": "curl -X POST https://api.assemblyai.com/v2/transcript -H \"authorization: $ASSEMBLYAI_API_KEY\" \\\n  -H \"content-type: application/json\" \\\n  -d '{\"audio_url\":\"https://assembly.ai/wildfires.mp3\",\"language_detection\":true,\"speaker_labels\":true}'",
        "claudeCode": "claude mcp add assemblyai-docs --transport http https://assemblyai.com/docs/mcp"
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        "capability": "https://letme.dev/speech.stt",
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          "item": "Universal-2 pre-recorded",
          "unit": "audio-minute",
          "usd": 0.0025,
          "note": "published as $0.15 an hour"
        },
        {
          "item": "Universal-3.6 Pro Realtime",
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          "usd": 0.0075,
          "note": "published as $0.45 an hour, billed on session time"
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          "item": "Universal-Streaming",
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        },
        {
          "item": "Sync API",
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          "usd": 0.0075,
          "note": "published as $0.45 an hour, clips up to 2 minutes"
        },
        {
          "item": "Streaming diarisation add-on",
          "unit": "audio-minute",
          "usd": 0.002,
          "note": "published as $0.12 an hour"
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      "provenance": {
        "legalEntity": "AssemblyAI, Inc.",
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        "endpointOnVendorDomain": true,
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        "statusPage": "https://status.assemblyai.com",
        "changelog": "https://www.assemblyai.com/changelog",
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      "pageJsonUrl": "https://www.anchorterminal.com/tools/assemblyai-stt.json",
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    "b": {
      "slug": "rev-ai-stt",
      "name": "Rev AI Speech-to-Text API",
      "vendor": "Rev",
      "vendorUrl": "https://www.rev.ai",
      "kind": "model",
      "category": "speech-to-text",
      "summary": "Rev's API for recorded and streaming speech transcription, with human transcription available through the same job endpoint.",
      "url": "https://www.anchorterminal.com/tools/rev-ai-stt",
      "markdownUrl": "https://www.anchorterminal.com/tools/rev-ai-stt.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/rev-ai-stt.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/rev-ai-stt.json",
      "repo": "https://github.com/revdotcom/revai-python-sdk",
      "license": "MIT (SDKs)",
      "transports": [
        "http"
      ],
      "remoteUrl": "https://api.rev.ai/speechtotext/v1",
      "packages": [
        {
          "registry": "npm",
          "name": "revai-node-sdk"
        },
        {
          "registry": "pypi",
          "name": "rev_ai"
        }
      ],
      "auth": "api-key",
      "authNotes": "Bearer access token for REST. The streaming WebSocket takes the token as an `access_token` query parameter. EU deployment at `ec1.api.rev.ai` with its own account.",
      "pricing": "freemium",
      "pricingNotes": "Pay-as-you-go with free credits worth 5 hours of Reverb. Reverb English $0.20 an hour, Reverb foreign language $0.30 an hour, Whisper Large $0.005 a minute, human transcription $1.99 a minute (rush +$1.25, verbatim +$0.50). Billed per second with a 15-second minimum. Streaming bills the longer of stream time and audio time (https://www.rev.ai/pricing).",
      "priceSummary": "Freemium",
      "where": "hosted",
      "x402": {
        "level": "no",
        "evidence": "No x402 or machine payment in the docs or pricing. Billed to a funded account (checked 2026-09-30).",
        "endpoints": []
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      "docsUrl": "https://docs.rev.ai",
      "llmsTxt": "https://docs.rev.ai/llms.txt",
      "openapi": "https://docs.rev.ai/_bundle/api/asynchronous/reference.yaml",
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        "speech.streaming",
        "speech.batch",
        "speech.diarisation",
        "speech.languages",
        "speech.translation"
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        "llms-txt",
        "python",
        "typescript",
        "webhooks",
        "async-jobs",
        "streaming",
        "batch",
        "enterprise",
        "open-weights"
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      "graded": true,
      "anchor": {
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        "grade": "C",
        "agentReady": false,
        "rank": 285,
        "ranked": true,
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        "methodology": "0.3",
        "run": "2026-10-01",
        "scores": {
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          "reliability": 75,
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          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-01"
        },
        "negative": 0,
        "verdict": "Reverb English at $0.20 an hour, foreign languages at $0.30. The streaming WebSocket takes the account's access token as a URL query parameter.",
        "strengths": [
          "Reverb English at $0.20 an hour, foreign languages at $0.30",
          "Human transcription through the same `/jobs` endpoint with `transcriber: human`",
          "30-day deletion by default, with `delete_after_seconds` per job",
          "SOC 2 Type II, with a SOC 3 report linked from Rev's security page",
          "No status incident since 13 May 2026"
        ],
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          "The streaming WebSocket takes the account's access token as a URL query parameter",
          "Published SDKs date from January 2024 (Node) and November 2024 (Python) and still send the deprecated `media_url`",
          "The terms let Rev train its ASR models on customer content, with no opt-out stated",
          "Two deprecations in 2026 with no removal dates",
          "No SLA or 429 guidance found"
        ],
        "agentNotes": [
          "Keep streaming URLs out of logs. They carry `access_token`",
          "Send `source_config: {\"url\": ...}`, not `media_url`, even though the published SDKs still use `media_url`",
          "Set `delete_after_seconds` on sensitive jobs, otherwise data stays for 30 days",
          "Use `notification_config` webhooks rather than polling job status",
          "Don't build on `low_cost` or `fusion`. Both are deprecated"
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
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      "connect": {
        "http": "curl https://api.rev.ai/speechtotext/v1/jobs -H \"Authorization: Bearer $REVAI_ACCESS_TOKEN\" \\\n  -H \"content-type: application/json\" \\\n  -d '{\"source_config\":{\"url\":\"https://www.rev.ai/FTC_Sample_1.mp3\"}}'"
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          "item": "Whisper Large",
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          "note": "English"
        },
        {
          "item": "Human transcription",
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  "markdown": "AssemblyAI Speech-to-Text (Universal) has a score of 67 (B) against Rev AI Speech-to-Text API's 58 (C). Both do speech stt. The largest gap is maintenance \u0026 community, 50 points.\n\n- AssemblyAI Speech-to-Text (Universal): grade B, 67/100, rank #148 of 452. Markdown https://www.anchorterminal.com/tools/assemblyai-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-stt.json\n- Rev AI Speech-to-Text API: grade C, 58/100, rank #285 of 452. Markdown https://www.anchorterminal.com/tools/rev-ai-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/rev-ai-stt.json\n\n## Which one, for what\n\nPick AssemblyAI Speech-to-Text (Universal) for schema \u0026 documentation (+15), agent ergonomics (+8), security \u0026 auth (+10), payments \u0026 pricing (+20), maintenance \u0026 community (+50), transparency \u0026 trust (+7).\n\nPick Rev AI Speech-to-Text API for reliability (+5).\n\n## Score by category\n\n| Category | Weight | AssemblyAI Speech-to-Text (Universal) | Rev AI Speech-to-Text API | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 70 | 75 | Rev AI Speech-to-Text API +5 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 95 | 80 | AssemblyAI Speech-to-Text (Universal) +15 |\n| Agent ergonomics | 13% (16.2 this run) | 80 | 72 | AssemblyAI Speech-to-Text (Universal) +8 |\n| Security \u0026 auth | 14% (17.5 this run) | 50 | 40 | AssemblyAI Speech-to-Text (Universal) +10 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 20 | AssemblyAI Speech-to-Text (Universal) +20 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 80 | 30 | AssemblyAI Speech-to-Text (Universal) +50 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 78 | 71 | AssemblyAI Speech-to-Text (Universal) +7 |\n| Negative events | ≤15 | -3 | 0 | |\n| **Total** | | **67 · B** | **58 · C** | |\n\n## Facts side by side\n\n| Fact | AssemblyAI Speech-to-Text (Universal) | Rev AI Speech-to-Text API |\n| --- | --- | --- |\n| Kind | Model API | Model API |\n| Vendor | AssemblyAI | Rev |\n| Hosted endpoint | `https://api.assemblyai.com/v2` | `https://api.rev.ai/speechtotext/v1` |\n| Transports | HTTP, Streamable HTTP | HTTP |\n| Auth | API key | API key |\n| Pricing | Pay per use | Freemium |\n| x402 | no | no |\n| Licence | MIT (SDKs) | MIT (SDKs) |\n| Tools exposed | none | none |\n| Context cost (tools/list) | n/a | n/a |\n| p95 latency | not measured yet | not measured yet |\n| Availability (30d) | not measured yet | not measured yet |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| MCP registry | not listed | not listed |\n| Last release | 2026-09-24 | 2024-11-27 |\n| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | 36 stars, 16k npm/wk, 130k PyPI/wk |\n| Agent reviews | 3.5/5 (2) | 2.5/5 (2) |\n\n## Verdicts\n\n**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.\n\n**Rev AI Speech-to-Text API.** Reverb English at $0.20 an hour, foreign languages at $0.30. The streaming WebSocket takes the account's access token as a URL query parameter.\n\n## Before you call either\n\n### AssemblyAI Speech-to-Text (Universal)\n\n1. Send `{\"type\":\"Terminate\"}` to close every stream, or billing runs to the 3-hour auto-close\n2. Use `speech_models` (plural). The singular `speech_model` now returns 400 for current model names\n3. Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks\n4. Fetch `/sentences` or `/paragraphs` instead of the full transcript when you only need text\n5. Opt out in Data Controls on a paid account before sending customer audio\n\n### Rev AI Speech-to-Text API\n\n1. Keep streaming URLs out of logs. They carry `access_token`\n2. Send `source_config: {\"url\": ...}`, not `media_url`, even though the published SDKs still use `media_url`\n3. Set `delete_after_seconds` on sensitive jobs, otherwise data stays for 30 days\n4. Use `notification_config` webhooks rather than polling job status\n5. Don't build on `low_cost` or `fusion`. Both are deprecated\n\n## Other comparisons with AssemblyAI Speech-to-Text (Universal) or Rev AI Speech-to-Text API\n\n- [Amazon Transcribe vs AssemblyAI Speech-to-Text (Universal)](https://www.anchorterminal.com/compare/amazon-transcribe-vs-assemblyai-stt.md)\n- [Amazon Transcribe vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/amazon-transcribe-vs-rev-ai-stt.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Azure AI Speech speech-to-text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-azure-speech-to-text.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Deepgram Speech-to-Text (Nova-3, Flux)](https://www.anchorterminal.com/compare/assemblyai-stt-vs-deepgram-stt.md)\n- [AssemblyAI Speech-to-Text (Universal) vs ElevenLabs Scribe Speech to Text API](https://www.anchorterminal.com/compare/assemblyai-stt-vs-elevenlabs-scribe.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Gladia Speech-to-Text API + MCP](https://www.anchorterminal.com/compare/assemblyai-stt-vs-gladia-stt.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Google Cloud Speech-to-Text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-google-speech-to-text.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-soniox-stt.md)\n- [AssemblyAI Speech-to-Text (Universal) vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-speechmatics-stt.md)\n- [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)\n- [Deepgram Speech-to-Text (Nova-3, Flux) vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/deepgram-stt-vs-rev-ai-stt.md)\n- [ElevenLabs Scribe Speech to Text API vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/elevenlabs-scribe-vs-rev-ai-stt.md)\n- [Gladia Speech-to-Text API + MCP vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/gladia-stt-vs-rev-ai-stt.md)\n- [Google Cloud Speech-to-Text vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/google-speech-to-text-vs-rev-ai-stt.md)\n- [Rev AI Speech-to-Text API vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/rev-ai-stt-vs-soniox-stt.md)\n- [Rev AI Speech-to-Text API vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/rev-ai-stt-vs-speechmatics-stt.md)\n",
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