{
  "data": {
    "a": {
      "slug": "cartesia-tts",
      "name": "Cartesia Sonic TTS API + MCP",
      "vendor": "Cartesia",
      "vendorUrl": "https://cartesia.ai",
      "kind": "model",
      "category": "text-to-speech",
      "summary": "Sonic text-to-speech, currently `sonic-3.6` in 44 languages, over `/tts/bytes`, `/tts/sse` and a WebSocket that takes streamed LLM text with contexts and word timestamps.",
      "url": "https://www.anchorterminal.com/tools/cartesia-tts",
      "markdownUrl": "https://www.anchorterminal.com/tools/cartesia-tts.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/cartesia-tts.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/cartesia-tts.json",
      "repo": "https://github.com/cartesia-ai/cartesia-python",
      "license": "Apache-2.0 (SDKs)",
      "transports": [
        "http",
        "streamable-http",
        "stdio"
      ],
      "remoteUrl": "https://api.cartesia.ai",
      "packages": [
        {
          "registry": "npm",
          "name": "@cartesia/cartesia-js"
        },
        {
          "registry": "pypi",
          "name": "cartesia"
        },
        {
          "registry": "pypi",
          "name": "cartesia-mcp"
        }
      ],
      "auth": "mixed",
      "authNotes": "`Authorization: Bearer` API key plus a required `Cartesia-Version` date header (currently `2026-08-14`). Browsers should use short-lived access tokens minted server-side. The hosted MCP at `https://mcp.cartesia.ai/mcp` signs in through the Playground and creates an MCP key. The local `cartesia-mcp` reads `CARTESIA_API_KEY`.",
      "pricing": "freemium",
      "pricingNotes": "TTS costs about 1 credit a character, charged only on successful requests. Free has 20,000 credits a month (about 27 minutes of Sonic 3.6), Pro $5 100,000, Startup $49 1.25M and Scale $299 8M. Overages, if enabled, cost $65 per 1M credits on Pro, $45 on Startup and $38 on Scale. Commercial use starts at Pro. Unused credits roll over up to 2 times the monthly amount (https://cartesia.ai/pricing).",
      "priceSummary": "$5 / mo",
      "where": "both",
      "x402": {
        "level": "no",
        "evidence": "No x402 or machine payment in the docs or pricing (checked 2026-09-30).",
        "endpoints": []
      },
      "toolCount": 15,
      "popularity": {
        "githubStars": 133,
        "npmWeekly": 166023,
        "pypiWeekly": 176771,
        "asOf": "2026-09-30"
      },
      "docsUrl": "https://docs.cartesia.ai/build-with-cartesia/tts-models/latest",
      "llmsTxt": "https://docs.cartesia.ai/llms.txt",
      "capabilities": [
        "speech.tts",
        "speech.streaming",
        "speech.voices",
        "speech.ssml",
        "speech.languages"
      ],
      "tags": [
        "hosted",
        "freemium",
        "free-tier",
        "closed-source",
        "python",
        "typescript",
        "llms-txt",
        "mcp",
        "streaming",
        "enterprise"
      ],
      "lastRelease": "2026-09-30",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 64.2,
        "grade": "B",
        "agentReady": false,
        "rank": 187,
        "ranked": true,
        "rankOf": 452,
        "categoryRank": 6,
        "methodology": "0.3",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 65,
          "maintenance": 79,
          "payments": 30,
          "reliability": 63,
          "schema": 86,
          "security": 58,
          "transparency": 71
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-01"
        },
        "negative": 0,
        "verdict": "WebSocket input accepts streamed LLM text with contexts, flushing and word timestamps. Five TTS incidents on the status page between 29 July and 21 August 2026.",
        "strengths": [
          "WebSocket input accepts streamed LLM text with contexts, flushing and word timestamps",
          "Dated model snapshots such as `sonic-3.6-2026-08-27` never change, and `Cartesia-Version` pins the API shape",
          "OpenAPI and AsyncAPI files per API version listed in llms.txt",
          "Short-lived access tokens with TTS, STT and agent grants for browser clients",
          "Deprecations dated in the changelog, Sonic-2 and Sonic Turbo sunset after 2026-10-20"
        ],
        "weaknesses": [
          "Five TTS incidents on the status page between 29 July and 21 August 2026",
          "TTS concurrency is 2 on Free, 3 on Pro, 5 on Startup and 15 on Scale",
          "The Terms allow training on inputs and outputs unless you opt out by form",
          "Zero data retention is Enterprise only",
          "No SLA, and no error responses documented for the TTS endpoints"
        ],
        "agentNotes": [
          "Send the `Cartesia-Version` header on every request.",
          "Pin a dated snapshot such as `sonic-3.6-2026-08-27` if output must not change.",
          "Move off `sonic-2`, `sonic-turbo` and `sonic-3-2025-10-27` before 2026-10-20.",
          "Expect a 429 at the plan's concurrency limit and queue requests yourself.",
          "Mint a short-lived access token for browser clients instead of shipping the API key."
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 2,
        "avgRating": 3,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "medium",
            "grade": "B",
            "methodology": "0.3",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 64.2
          }
        ],
        "editorialScores": {
          "ergonomics": 65,
          "maintenance": 79,
          "payments": 30,
          "reliability": 63,
          "schema": 86,
          "security": 58,
          "transparency": 60
        },
        "provenanceScore": 82
      },
      "connect": {
        "http": "curl -X POST https://api.cartesia.ai/tts/bytes -H \"Authorization: Bearer $CARTESIA_API_KEY\" \\\n  -H \"Cartesia-Version: 2026-08-14\" -H \"content-type: application/json\" -o speech.wav \\\n  -d '{\"model_id\":\"sonic-3.6\",\"transcript\":\"Your table is booked for seven.\",\"voice\":{\"id\":\"47c38ca4-5f35-497b-b1a3-415245fb35e1\"},\"output_format\":{\"container\":\"wav\",\"encoding\":\"pcm_s16le\",\"sample_rate\":44100}}'",
        "claudeCode": "claude mcp add --transport http --scope user cartesia https://mcp.cartesia.ai/mcp",
        "config": {
          "mcpServers": {
            "cartesia": {
              "args": [
                "cartesia-mcp"
              ],
              "command": "uvx",
              "env": {
                "CARTESIA_API_KEY": "${CARTESIA_API_KEY}"
              }
            }
          }
        }
      },
      "letme": {
        "capability": "https://letme.dev/speech.tts",
        "tool": "https://letme.dev/cartesia-tts"
      },
      "sameCompany": [
        "cartesia-voice-cloning"
      ],
      "area": "voice",
      "unitPrices": [
        {
          "item": "Sonic TTS overage on Pro",
          "unit": "1m-chars",
          "usd": 65,
          "note": "about 1 credit a character, $65 per 1M credits"
        },
        {
          "item": "Sonic TTS overage on Startup",
          "unit": "1m-chars",
          "usd": 45
        },
        {
          "item": "Sonic TTS overage on Scale",
          "unit": "1m-chars",
          "usd": 38
        },
        {
          "item": "Pro plan",
          "unit": "month",
          "usd": 5,
          "note": "100,000 credits"
        },
        {
          "item": "Startup plan",
          "unit": "month",
          "usd": 49,
          "note": "1.25M credits"
        },
        {
          "item": "Scale plan",
          "unit": "month",
          "usd": 299,
          "note": "8M credits"
        }
      ],
      "provenance": {
        "legalEntity": "Cartesia AI, Inc.",
        "domain": "cartesia.ai",
        "domainRegistered": "2023-05-10",
        "endpointOnVendorDomain": true,
        "terms": "https://www.cartesia.ai/legal/terms",
        "privacy": "https://www.cartesia.ai/legal/privacy",
        "statusPage": "https://status.cartesia.ai",
        "changelog": "https://docs.cartesia.ai/changelog/2026",
        "securityTxt": "none",
        "checked": "2026-09-30",
        "score": 82
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/cartesia-tts.json",
      "live": {
        "slug": "cartesia-tts",
        "probe": {
          "target": "https://api.cartesia.ai",
          "method": "get",
          "lastAt": "2026-10-04T23:48:06.28751768Z",
          "lastOk": true,
          "lastStatus": 200,
          "lastMs": 53,
          "authRequired": false,
          "uptime24h": 100,
          "uptime30d": 100,
          "p50ms24h": 61,
          "p95ms24h": 137,
          "samples24h": 272,
          "samples30d": 1100,
          "days": [
            {
              "date": "2026-09-30",
              "probes": 35,
              "ok": 35
            },
            {
              "date": "2026-10-01",
              "probes": 276,
              "ok": 276
            },
            {
              "date": "2026-10-02",
              "probes": 248,
              "ok": 248
            },
            {
              "date": "2026-10-03",
              "probes": 271,
              "ok": 271
            },
            {
              "date": "2026-10-04",
              "probes": 270,
              "ok": 270
            }
          ]
        },
        "vendorStatus": {
          "page": "https://status.cartesia.ai",
          "indicator": "none",
          "summary": "All Systems Operational",
          "checkedAt": "2026-10-04T23:49:06.943209758Z"
        },
        "versions": [
          {
            "registry": "github",
            "name": "cartesia-ai/cartesia-python",
            "version": "v4.2.0",
            "released": "2026-09-02",
            "seenAt": "2026-10-04T16:23:11.882857509Z"
          },
          {
            "registry": "npm",
            "name": "@cartesia/cartesia-js",
            "version": "4.2.0",
            "seenAt": "2026-10-04T16:23:08.936594762Z"
          },
          {
            "registry": "pypi",
            "name": "cartesia",
            "version": "4.2.0",
            "released": "2026-09-02",
            "seenAt": "2026-10-04T16:23:09.798087978Z"
          },
          {
            "registry": "pypi",
            "name": "cartesia-mcp",
            "version": "0.26.0",
            "released": "2026-09-30",
            "seenAt": "2026-10-04T16:23:09.984461576Z"
          }
        ],
        "githubStars": 133,
        "npmWeekly": 108942,
        "pypiWeekly": 188249,
        "securityTxt": {
          "url": "https://cartesia.ai/.well-known/security.txt",
          "state": "valid",
          "expires": "2027-10-03T00:00:00.000Z",
          "checkedAt": "2026-10-04T15:15:57.920556028Z"
        },
        "llmsTxt": {
          "url": "https://docs.cartesia.ai/llms.txt",
          "ok": true,
          "status": 200,
          "checkedAt": "2026-10-04T15:17:23.748277625Z"
        },
        "domain": {
          "domain": "cartesia.ai",
          "registered": "2023-05-10",
          "source": "https://rdap.identitydigital.services/rdap/domain/cartesia.ai",
          "checkedAt": "2026-10-04T13:04:05.26596839Z"
        },
        "pages": [
          {
            "url": "https://docs.cartesia.ai/changelog/2026",
            "kind": "changelog",
            "status": 200,
            "checkedAt": "2026-10-04T15:43:22.154553148Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "56a07dda1f5d"
          },
          {
            "url": "https://cartesia.ai/pricing",
            "kind": "pricing",
            "status": 200,
            "checkedAt": "2026-10-04T15:41:44.64571005Z",
            "changedAt": "2026-10-03T15:29:56.901063562Z",
            "fingerprint": "3e49bcd49fcf"
          },
          {
            "url": "https://www.cartesia.ai/legal/privacy",
            "kind": "privacy",
            "status": 200,
            "checkedAt": "2026-10-04T15:49:41.751185158Z",
            "changedAt": "2026-10-03T15:37:37.717663201Z",
            "fingerprint": "6fea00c7255f"
          },
          {
            "url": "https://www.cartesia.ai/legal/terms",
            "kind": "terms",
            "status": 200,
            "checkedAt": "2026-10-04T15:49:43.846741137Z",
            "changedAt": "2026-10-03T15:37:39.779484537Z",
            "fingerprint": "c899e30661ba"
          }
        ],
        "updatedAt": "2026-10-04T23:49:06.943209758Z"
      }
    },
    "b": {
      "slug": "soniox-tts",
      "name": "Soniox Text-to-Speech",
      "vendor": "Soniox",
      "vendorUrl": "https://soniox.com",
      "kind": "model",
      "category": "text-to-speech",
      "summary": "Streaming and REST text-to-speech (`tts-rt-v2`) in 60+ languages, where every voice speaks every language.",
      "url": "https://www.anchorterminal.com/tools/soniox-tts",
      "markdownUrl": "https://www.anchorterminal.com/tools/soniox-tts.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/soniox-tts.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/soniox-tts.json",
      "repo": "https://github.com/soniox/soniox-python",
      "license": "Apache-2.0 (Python SDK)",
      "transports": [
        "http"
      ],
      "remoteUrl": "https://tts-rt.soniox.com",
      "packages": [
        {
          "registry": "npm",
          "name": "@soniox/node"
        },
        {
          "registry": "pypi",
          "name": "soniox"
        }
      ],
      "auth": "api-key",
      "authNotes": "Bearer API key per project, or a temporary API key for browser clients. REST at `POST https://tts-rt.soniox.com/tts`, WebSocket at `wss://tts-rt.soniox.com/tts-websocket`. Regional hosts for the EU, Japan and India.",
      "pricing": "usage",
      "pricingNotes": "Token-based pay-as-you-go. Input text $4.00 per 1M tokens and output audio $21.50 per 1M tokens, which Soniox puts at about $0.70 an hour of generated speech (1 character is about 0.3 input tokens, 1 hour of audio about 30,000 output tokens). No free credits for new sign-ups (https://soniox.com/pricing).",
      "priceSummary": "Pay per use",
      "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": []
      },
      "toolCount": null,
      "popularity": {
        "githubStars": 12,
        "npmWeekly": 22200,
        "pypiWeekly": null,
        "asOf": "2026-09-30"
      },
      "docsUrl": "https://soniox.com/docs/tts/get-started",
      "llmsTxt": "https://soniox.com/docs/llms.txt",
      "capabilities": [
        "speech.tts",
        "speech.streaming",
        "speech.voices",
        "speech.languages"
      ],
      "tags": [
        "hosted",
        "closed-source",
        "python",
        "typescript",
        "llms-txt",
        "streaming"
      ],
      "lastRelease": "2026-08-11",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 63.9,
        "grade": "B",
        "agentReady": false,
        "rank": 193,
        "ranked": true,
        "rankOf": 452,
        "categoryRank": 7,
        "methodology": "0.3",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 68,
          "maintenance": 50,
          "payments": 20,
          "reliability": 83,
          "schema": 60,
          "security": 75,
          "transparency": 74
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-01"
        },
        "negative": 0,
        "verdict": "The security page states that content is not stored by default or used for training. Audio output is capped at two minutes per request or stream.",
        "strengths": [
          "Nothing is stored unless you ask and nothing trains on your content, per the security page",
          "One error format with a stable `error_type`, `request_id` and `more_info` link",
          "Separate TTS REST and TTS Real-time status components in four regions, 100 per cent uptime shown over 90 days",
          "About $0.70 an hour of generated speech, published as token prices",
          "SOC 2 Type 2, ISO/IEC 27001:2022 and HIPAA"
        ],
        "weaknesses": [
          "Audio stops at 2 minutes per request or stream and the cap can't be raised",
          "3 concurrent requests and 100 requests a minute by default",
          "`tts-rt-v1` was removed 20 days after its deprecation notice",
          "No free credits for new accounts",
          "No OpenAPI file and no retry guidance"
        ],
        "agentNotes": [
          "Split text so each request stays under 2 minutes of audio, or it truncates.",
          "Branch on `error_type`, not the message, and back off on `limit_exceeded`.",
          "Use a temporary API key for browser clients.",
          "Use bracketed audio tags such as `[whispering]` instead of SSML.",
          "Pick the regional host (EU, Japan, India) that matches your data residency."
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 2,
        "avgRating": 3,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "medium",
            "grade": "B",
            "methodology": "0.3",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 63.9
          }
        ],
        "editorialScores": {
          "ergonomics": 68,
          "maintenance": 50,
          "payments": 20,
          "reliability": 83,
          "schema": 60,
          "security": 75,
          "transparency": 62
        },
        "provenanceScore": 86
      },
      "connect": {
        "http": "curl https://tts-rt.soniox.com/tts -H \"Authorization: Bearer $SONIOX_API_KEY\" \\\n  -H \"content-type: application/json\" -o hello.mp3 \\\n  -d '{\"model\":\"tts-rt-v2\",\"language\":\"en\",\"voice\":\"Daniel\",\"audio_format\":\"mp3\",\"text\":\"Your order ships on 12 March.\"}'"
      },
      "letme": {
        "capability": "https://letme.dev/speech.tts",
        "tool": "https://letme.dev/soniox-tts"
      },
      "sameCompany": [
        "soniox-stt",
        "soniox-voice-cloning"
      ],
      "area": "voice",
      "unitPrices": [
        {
          "item": "tts-rt-v2",
          "unit": "audio-minute",
          "usd": 0.0117,
          "note": "per minute of generated speech, Soniox's estimate of $0.70 an hour, token-billed"
        }
      ],
      "provenance": {
        "legalEntity": "Soniox Inc.",
        "domain": "soniox.com",
        "domainRegistered": "2020-03-23",
        "endpointOnVendorDomain": true,
        "terms": "https://soniox.com/policies/terms-of-service",
        "privacy": "https://soniox.com/policies/privacy-policy",
        "statusPage": "https://status.soniox.com",
        "changelog": "https://soniox.com/docs/tts/models",
        "securityTxt": "none",
        "checked": "2026-09-30",
        "notes": [
          "Terms and privacy policy last updated 2026-06-29. The company address is Foster City, California"
        ],
        "score": 86
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/soniox-tts.json",
      "live": {
        "slug": "soniox-tts",
        "probe": {
          "target": "https://tts-rt.soniox.com",
          "method": "get",
          "lastAt": "2026-10-04T23:48:16.154092205Z",
          "lastOk": true,
          "lastStatus": 404,
          "lastMs": 341,
          "authRequired": false,
          "uptime24h": 100,
          "uptime30d": 100,
          "p50ms24h": 313,
          "p95ms24h": 392,
          "samples24h": 272,
          "samples30d": 1100,
          "days": [
            {
              "date": "2026-09-30",
              "probes": 35,
              "ok": 35
            },
            {
              "date": "2026-10-01",
              "probes": 276,
              "ok": 276
            },
            {
              "date": "2026-10-02",
              "probes": 248,
              "ok": 248
            },
            {
              "date": "2026-10-03",
              "probes": 271,
              "ok": 271
            },
            {
              "date": "2026-10-04",
              "probes": 270,
              "ok": 270
            }
          ]
        },
        "vendorStatus": {
          "page": "https://status.soniox.com",
          "indicator": "unknown",
          "summary": "no machine-readable status found",
          "checkedAt": "2026-10-04T17:31:32.080499897Z"
        },
        "versions": [
          {
            "registry": "npm",
            "name": "@soniox/node",
            "version": "2.3.0",
            "seenAt": "2026-10-04T16:40:15.547086792Z"
          },
          {
            "registry": "pypi",
            "name": "soniox",
            "version": "2.10.0",
            "released": "2026-10-02",
            "seenAt": "2026-10-04T16:40:15.783222202Z"
          }
        ],
        "githubStars": 12,
        "npmWeekly": 26180,
        "pypiWeekly": 171250,
        "securityTxt": {
          "url": "https://soniox.com/.well-known/security.txt",
          "state": "none",
          "checkedAt": "2026-10-04T15:15:59.988207849Z"
        },
        "llmsTxt": {
          "url": "https://soniox.com/docs/llms.txt",
          "ok": true,
          "status": 200,
          "checkedAt": "2026-10-04T15:18:16.442369832Z"
        },
        "domain": {
          "domain": "soniox.com",
          "registered": "2020-03-23",
          "source": "https://rdap.verisign.com/com/v1/domain/soniox.com",
          "checkedAt": "2026-10-04T13:05:00.531232044Z"
        },
        "pages": [
          {
            "url": "https://soniox.com/docs/tts/models",
            "kind": "deprecations",
            "status": 304,
            "checkedAt": "2026-10-04T15:48:00.470722045Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "a63d4a072013"
          }
        ],
        "updatedAt": "2026-10-04T23:48:16.154092205Z"
      }
    },
    "summary": "Cartesia Sonic TTS API + MCP has a score of 64.2 (B) against Soniox Text-to-Speech's 63.9 (B). Both do speech tts. The largest gap is maintenance \u0026 community, 29 points."
  },
  "kind": "anchor.page",
  "links": {
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  "markdown": "Cartesia Sonic TTS API + MCP has a score of 64.2 (B) against Soniox Text-to-Speech's 63.9 (B). Both do speech tts. The largest gap is maintenance \u0026 community, 29 points.\n\n- Cartesia Sonic TTS API + MCP: grade B, 64.2/100, rank #187 of 452. Markdown https://www.anchorterminal.com/tools/cartesia-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/cartesia-tts.json\n- Soniox Text-to-Speech: grade B, 63.9/100, rank #193 of 452. Markdown https://www.anchorterminal.com/tools/soniox-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/soniox-tts.json\n\n## Which one, for what\n\nPick Cartesia Sonic TTS API + MCP for schema \u0026 documentation (+26), payments \u0026 pricing (+10), maintenance \u0026 community (+29).\n\nPick Soniox Text-to-Speech for reliability (+20), security \u0026 auth (+17).\n\n## Score by category\n\n| Category | Weight | Cartesia Sonic TTS API + MCP | Soniox Text-to-Speech | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 63 | 83 | Soniox Text-to-Speech +20 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 86 | 60 | Cartesia Sonic TTS API + MCP +26 |\n| Agent ergonomics | 13% (16.2 this run) | 65 | 68 | Soniox Text-to-Speech +3 |\n| Security \u0026 auth | 14% (17.5 this run) | 58 | 75 | Soniox Text-to-Speech +17 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 30 | 20 | Cartesia Sonic TTS API + MCP +10 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 79 | 50 | Cartesia Sonic TTS API + MCP +29 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 71 | 74 | Soniox Text-to-Speech +3 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **64.2 · B** | **63.9 · B** | |\n\n## Facts side by side\n\n| Fact | Cartesia Sonic TTS API + MCP | Soniox Text-to-Speech |\n| --- | --- | --- |\n| Kind | Model API | Model API |\n| Vendor | Cartesia | Soniox |\n| Hosted endpoint | `https://api.cartesia.ai` | `https://tts-rt.soniox.com` |\n| Transports | HTTP, Streamable HTTP, stdio | HTTP |\n| Auth | OAuth or key | API key |\n| Pricing | Freemium | Pay per use |\n| x402 | no | no |\n| Licence | Apache-2.0 (SDKs) | Apache-2.0 (Python SDK) |\n| Tools exposed | 15 | 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 | 2026-09-30 | 2026-08-11 |\n| Popularity | 133 stars, 166k npm/wk, 177k PyPI/wk | 12 stars, 22k npm/wk |\n| Agent reviews | 3/5 (2) | 3/5 (2) |\n\n## Verdicts\n\n**Cartesia Sonic TTS API + MCP.** WebSocket input accepts streamed LLM text with contexts, flushing and word timestamps. Five TTS incidents on the status page between 29 July and 21 August 2026.\n\n**Soniox Text-to-Speech.** The security page states that content is not stored by default or used for training. Audio output is capped at two minutes per request or stream.\n\n## Before you call either\n\n### Cartesia Sonic TTS API + MCP\n\n1. Send the `Cartesia-Version` header on every request.\n2. Pin a dated snapshot such as `sonic-3.6-2026-08-27` if output must not change.\n3. Move off `sonic-2`, `sonic-turbo` and `sonic-3-2025-10-27` before 2026-10-20.\n4. Expect a 429 at the plan's concurrency limit and queue requests yourself.\n5. Mint a short-lived access token for browser clients instead of shipping the API key.\n\n### Soniox Text-to-Speech\n\n1. Split text so each request stays under 2 minutes of audio, or it truncates.\n2. Branch on `error_type`, not the message, and back off on `limit_exceeded`.\n3. Use a temporary API key for browser clients.\n4. Use bracketed audio tags such as `[whispering]` instead of SSML.\n5. Pick the regional host (EU, Japan, India) that matches your data residency.\n\n## Other comparisons with Cartesia Sonic TTS API + MCP or Soniox Text-to-Speech\n\n- [Amazon Polly vs Cartesia Sonic TTS API + MCP](https://www.anchorterminal.com/compare/amazon-polly-vs-cartesia-tts.md)\n- [Amazon Polly vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/amazon-polly-vs-soniox-tts.md)\n- [Azure AI Speech text-to-speech vs Cartesia Sonic TTS API + MCP](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-cartesia-tts.md)\n- [Azure AI Speech text-to-speech vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-soniox-tts.md)\n- [Cartesia Sonic TTS API + MCP vs Deepgram Text-to-Speech (Aura-2, Flux TTS)](https://www.anchorterminal.com/compare/cartesia-tts-vs-deepgram-tts.md)\n- [Cartesia Sonic TTS API + MCP vs ElevenLabs Text to Speech API + MCP](https://www.anchorterminal.com/compare/cartesia-tts-vs-elevenlabs-tts.md)\n- [Cartesia Sonic TTS API + MCP vs Murf TTS API + MCP](https://www.anchorterminal.com/compare/cartesia-tts-vs-murf-tts.md)\n- [Cartesia Sonic TTS API + MCP vs PlayHT Text-to-Speech API](https://www.anchorterminal.com/compare/cartesia-tts-vs-playht-tts.md)\n- [Cartesia Sonic TTS API + MCP vs Resemble AI Text-to-Speech API](https://www.anchorterminal.com/compare/cartesia-tts-vs-resemble-ai-tts.md)\n- [Cartesia Sonic TTS API + MCP vs Rime TTS API + MCP](https://www.anchorterminal.com/compare/cartesia-tts-vs-rime-tts.md)\n- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/deepgram-tts-vs-soniox-tts.md)\n- [ElevenLabs Text to Speech API + MCP vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/elevenlabs-tts-vs-soniox-tts.md)\n- [Murf TTS API + MCP vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/murf-tts-vs-soniox-tts.md)\n- [PlayHT Text-to-Speech API vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/playht-tts-vs-soniox-tts.md)\n- [Resemble AI Text-to-Speech API vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/resemble-ai-tts-vs-soniox-tts.md)\n- [Rime TTS API + MCP vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/rime-tts-vs-soniox-tts.md)\n",
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    "description": "Cartesia Sonic TTS API + MCP has a score of 64.2 (B) against Soniox Text-to-Speech's 63.9 (B). Both do speech tts. The largest gap is maintenance \u0026 community, 29 points. Category scores, facts, verdicts and agent notes side by side.",
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