{ "data": { "a": { "slug": "inworld-voice-cloning", "name": "Inworld Instant Voice Cloning", "vendor": "Inworld AI", "vendorUrl": "https://inworld.ai", "kind": "model", "category": "voice-cloning", "summary": "Inworld's Instant Voice Cloning API makes a reusable text-to-speech voice from 3 to 30 seconds of audio in one synchronous call, for Inworld's TTS-2 models. The same operation is in the Inworld CLI and its bundled MCP server.", "url": "https://www.anchorterminal.com/tools/inworld-voice-cloning", "markdownUrl": "https://www.anchorterminal.com/tools/inworld-voice-cloning.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/inworld-voice-cloning.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/inworld-voice-cloning.json", "dns": "inworld-voice-cloning.grade.anchorterminal.com", "repo": "https://github.com/inworld-ai/inworld-api-examples", "license": "Proprietary service under Inworld's Terms of Service. The `@inworld/cli` and `@inworld/tts` npm packages and the examples repository are MIT", "transports": [ "http", "stdio", "streamable-http" ], "remoteUrl": "https://api.inworld.ai", "packages": [ { "registry": "npm", "name": "@inworld/cli" }, { "registry": "npm", "name": "@inworld/tts" }, { "registry": "pypi", "name": "inworld-tts" } ], "auth": "api-key", "authNotes": "Self-serve workspace API key from the Portal or `inworld workspace add-key`, sent as `Authorization: Basic` with the Base64 credential as copied. Keys are read-only for the Voice API by default, and cloning, updating and deleting voices need the write toggle, which can be changed on an existing key. Deleting a key revokes it. One-time tokens minted from a key serve browser and mobile clients.", "pricing": "freemium", "pricingNotes": "Creating an instant clone has no charge in the docs or on the pricing page. Speech from a clone costs $25 per million characters on TTS-2 or $15 on TTS-2 Flash on the free On-Demand plan, falling on the $25, $100, $300 and $1,500 monthly plans. On-Demand allows 100 custom voices and 2 cloning requests a minute (checked 2026-11-06).", "priceSummary": "$25 / mo", "where": "both", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the docs, llms.txt or the pricing page (checked 2026-11-06). Credits are bought at a checkout page, $10 minimum.", "endpoints": [] }, "toolCount": 40, "popularity": { "githubStars": null, "npmWeekly": 3632, "pypiWeekly": null, "asOf": "2026-11-06" }, "docsUrl": "https://docs.inworld.ai/tts/instant-voice-cloning", "llmsTxt": "https://docs.inworld.ai/llms.txt", "capabilities": [ "voice.clone", "voice.design", "speech.tts" ], "tags": [ "hosted", "official", "freemium", "free-tier", "no-card", "closed-source", "python", "typescript", "llms-txt", "mcp", "cli", "status-page", "soc2" ], "lastRelease": "2026-10-29", "graded": true, "anchor": { "graded": true, "score": 61.9, "grade": "C", "agentReady": false, "rank": 588, "ranked": true, "rankOf": 1510, "categoryRank": 4, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 64, "maintenance": 68, "payments": 40, "reliability": 75, "schema": 64, "security": 55, "transparency": 63 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-11-06" }, "negative": 0, "verdict": "One JSON call returns a usable voice ID from 3 to 30 seconds of audio, with no charge per clone and 100 custom voices on the free plan, behind keys that are read-only until write access is switched on. The API has no consent field, and Zero Data Retention excludes cloning samples.", "bestFor": "Teams already using Inworld TTS-2 that want clones from a short clip through one call, the CLI or MCP.", "strengths": [ "Synchronous clone from 3 to 30 seconds of WAV or MP3 audio, with language auto-detection and optional background-noise removal", "No charge per clone. The free On-Demand plan includes instant cloning and 100 custom voices, and speech is $25 per million characters on TTS-2", "API keys are read-only by default. Cloning, updating and deleting voices need a write toggle that can be changed on an existing key", "`GET /voices/v1/voices` filters by `source = \"IVC\"` with paging, and `voices:customVoiceCapacity` reports how many custom voices remain", "`llms.txt`, `llms-full.txt` and a Markdown twin of every docs page, plus `clone_voice` in the MCP server in `@inworld/cli` 1.5.0 (29 October 2026)" ], "weaknesses": [ "No consent, verification or watermark field in the clone API. Only the Portal flow asks the user to confirm rights to the voice", "Zero Data Retention does not cover cloning audio samples, and no retention period for them was found", "No idempotency key on `POST /voices/v1/voices:clone`, and no error list for the Voice API", "No OpenAPI file is linked from the docs, and the repositories named in the npm metadata of the CLI and Node SDK are not public", "The MCP `clone_voice` description says about 5 seconds and 4 MB a sample, while the docs say 3 seconds and 12 MB" ], "agentNotes": [ "Create the key with write access (`inworld workspace add-key --write`). A default key gets code 7, insufficient access level, on `voices:clone`", "Send the complete Base64 credential as `Authorization: Basic $INWORLD_API_KEY`. Don't encode it again", "Send one 10 to 30 second WAV or MP3 clip as base64 in `voiceSamples[].audioData`. Audio past 30 seconds is cut", "Don't blind-retry a clone. There's no idempotency key, so list voices with `filter=source=\"IVC\"` first, and back off with jitter on 429", "Set `gender`, `ageGroup` and `categories` with UpdateVoice afterwards. The clone call ignores them without an error", "The response echoes up to 15 seconds of processed audio as base64 in `audioSamplesValidated`. Drop it before passing the result to a model" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 0, "avgRating": 0, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "C", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 61.9 } ], "editorialScores": { "ergonomics": 64, "maintenance": 68, "payments": 40, "reliability": 75, "schema": 64, "security": 55, "transparency": 51 }, "provenanceScore": 75, "checked": { "categories": { "ergonomics": "2026-11-06", "maintenance": "2026-11-06", "payments": "2026-11-06", "reliability": "2026-11-06", "schema": "2026-11-06", "security": "2026-11-06", "transparency": "2026-11-06" }, "last": "2026-11-06", "oldest": "2026-11-06", "stale": false, "staleAfterDays": 90 } }, "connect": { "install": "npm install -g @inworld/cli", "http": "curl --location 'https://api.inworld.ai/voices/v1/voices:clone' \\\n --header \"Authorization: Basic $INWORLD_API_KEY\" \\\n --header 'Content-Type: application/json' \\\n --data '{\"displayName\": \"my_voice_clone_demo\", \"languageCode\": \"en-US\", \"voiceSamples\": [{\"audioData\": \"\u003cbase64-audio-data\u003e\"}]}'", "claudeCode": "claude mcp add inworld -- inworld mcp", "config": { "mcpServers": { "Inworld": { "args": [ "mcp" ], "command": "inworld" } } } }, "letme": { "capability": "https://letme.dev/voice.clone", "tool": "https://letme.dev/inworld-voice-cloning" }, "sameCompany": [ "inworld-stt", "inworld-tts", "inworld-realtime" ], "area": "voice", "unitPrices": [ { "item": "Speech from a clone, TTS-2, On-Demand", "unit": "1m-chars", "usd": 25, "note": "$20, $17.50, $15 and $12.50 on the monthly plans" }, { "item": "Speech from a clone, TTS-2 Flash, On-Demand", "unit": "1m-chars", "usd": 15, "note": "$10 down to $7 on the monthly plans" }, { "item": "Creator plan", "unit": "month", "usd": 25, "note": "credits equal to the price, 500 custom voices, 3 clone requests a minute" }, { "item": "Builder plan", "unit": "month", "usd": 100, "note": "3,000 custom voices, 5 clone requests a minute" }, { "item": "Developer plan", "unit": "month", "usd": 300, "note": "10,000 custom voices, 10 clone requests a minute" }, { "item": "Growth plan", "unit": "month", "usd": 1500, "note": "30,000 custom voices, 20 clone requests a minute" } ], "provenance": { "legalEntity": "Theai, Inc. dba Inworld AI", "domain": "inworld.ai", "domainRegistered": "", "endpointOnVendorDomain": true, "terms": "https://inworld.ai/terms", "privacy": "https://inworld.ai/privacy", "statusPage": "https://status.inworld.ai", "changelog": "https://docs.inworld.ai/release-notes/tts", "securityTxt": "none", "checked": "2026-11-06", "notes": [ "The Terms of Service (effective 11 June 2025, re-read 6 November 2026) are an agreement with Theai, Inc. dba Inworld AI under California law. They carry no clause on robots or automated access, and none specific to voice cloning.", "inworld.ai's robots.txt carries `Content-Signal: ai-train=no, search=yes, ai-input=no`, recorded as a fact about the site. Since 30 October 2026 this is not a reason to hold, so this listing, held on 9 October for it, is graded.", "status.inworld.ai draws incidents from GitHub issues in inworld-ai/inworld-issue-status, read through the GitHub API on 6 November.", "inworld.ai/.well-known/security.txt returned 404 on 30 October per the inworld-tts check. The security page links a vulnerability report form." ], "score": 75 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/inworld-voice-cloning.json", "live": { "slug": "inworld-voice-cloning", "probe": { "target": "https://api.inworld.ai", "method": "get", "lastAt": "2026-11-07T19:22:14.002705937Z", "lastOk": true, "lastStatus": 200, "lastMs": 152, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 137, "p95ms24h": 266, "samples24h": 210, "samples30d": 210, "days": [ { "date": "2026-11-06", "probes": 13, "ok": 13 }, { "date": "2026-11-07", "probes": 197, "ok": 197 } ] }, "versions": [ { "registry": "npm", "name": "@inworld/cli", "version": "1.5.0", "seenAt": "2026-11-06T23:35:10.767231519Z" }, { "registry": "npm", "name": "@inworld/tts", "version": "1.1.1", "seenAt": "2026-11-06T23:35:12.902766977Z" }, { "registry": "pypi", "name": "inworld-tts", "version": "1.2.1", "released": "2026-05-06", "seenAt": "2026-11-06T23:35:14.803764179Z" } ], "githubStars": 66, "npmWeekly": 290, "pypiWeekly": 4010, "securityTxt": { "url": "https://inworld.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:01:11.794771951Z" }, "llmsTxt": { "url": "https://docs.inworld.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:32:51.758972379Z" }, "updatedAt": "2026-11-07T19:22:14.002705937Z" } }, "answer": "Inworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories.", "b": { "slug": "ultravox-voice-cloning", "name": "Ultravox Voice Cloning", "vendor": "Ultravox (Fixie.ai)", "vendorUrl": "https://www.ultravox.ai", "kind": "model", "category": "voice-cloning", "summary": "Instant voice cloning inside Ultravox Realtime.", "url": "https://www.anchorterminal.com/tools/ultravox-voice-cloning", "markdownUrl": "https://www.anchorterminal.com/tools/ultravox-voice-cloning.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/ultravox-voice-cloning.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json", "dns": "ultravox-voice-cloning.grade.anchorterminal.com", "transports": [ "http" ], "remoteUrl": "https://api.ultravox.ai/api", "packages": [], "auth": "api-key", "authNotes": "`X-API-Key` header, the same key as the rest of the Ultravox API.", "pricing": "freemium", "pricingNotes": "No separate cloning fee. Pay as you go includes 1 cloned voice and Pro ($100 a month, annual rate) includes 5, with speech from the clone billed inside calls at the standard $0.05 a minute. More clones are by request (https://www.ultravox.ai/pricing).", "priceSummary": "$100 / mo", "where": "hosted", "x402": { "level": "no", "evidence": "No x402 support in the docs, pricing page or MCP docs (checked 2026-09-30).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": null, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-09-30" }, "docsUrl": "https://docs.ultravox.ai/voices/cloning", "llmsTxt": "https://docs.ultravox.ai/llms.txt", "openapi": "https://api.ultravox.ai/api/schema/", "capabilities": [ "voice.clone", "speech.tts" ], "tags": [ "hosted", "closed-source", "no-card", "llms-txt", "openapi" ], "lastRelease": "2025-12-03", "graded": true, "anchor": { "graded": true, "score": 40.9, "grade": "E", "agentReady": false, "rank": 1311, "ranked": true, "rankOf": 1510, "categoryRank": 14, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 35, "maintenance": 5, "payments": 40, "reliability": 40, "schema": 68, "security": 35, "transparency": 53 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-01" }, "negative": 0, "verdict": "One multipart request with a 30 to 60 second sample. No consent or speaker verification, only a warranty in the terms.", "bestFor": "Giving an Ultravox voice agent a custom voice.", "strengths": [ "One multipart request with a 30 to 60 second sample", "No fee on top of the $0.05 a minute call rate", "One clone on the free Pay as You Go plan with 30 free minutes", "Voices are private to the creating account", "Call History records each call that uses the voice" ], "weaknesses": [ "No consent or speaker verification, only a warranty in the terms", "Clones work only inside Ultravox calls", "No documented errors, retry guidance or REST SDK", "Changelog's newest entry is 2025-12-03", "Docs say one clone per account, the pricing page says five on Pro" ], "agentNotes": [ "Send a single clean, single-speaker MP3 or WAV of 30 to 60 seconds, 10 MB at most", "Expect one clone per account unless support raises it, whatever the plan page says", "Test the voice in the Playground before putting it on a live agent", "Get the speaker's written consent first, the terms require it and Ultravox doesn't check" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 2, "avgRating": 2.5, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "E", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 40.9 } ], "editorialScores": { "ergonomics": 35, "maintenance": 5, "payments": 40, "reliability": 40, "schema": 68, "security": 35, "transparency": 25 }, "provenanceScore": 81, "checked": { "categories": { "ergonomics": "2026-10-01", "maintenance": "2026-10-01", "payments": "2026-10-01", "reliability": "2026-10-01", "schema": "2026-10-01", "security": "2026-10-01", "transparency": "2026-10-01" }, "last": "2026-10-01", "lastMoved": "2026-10-27", "oldest": "2026-10-01", "stale": false, "staleAfterDays": 90 } }, "connect": { "http": "curl -X POST https://api.ultravox.ai/api/voices -H \"X-API-Key: $ULTRAVOX_API_KEY\" \\\n -F 'file=@sample.wav' -F 'name=Support voice' -F 'language=en-US'" }, "letme": { "capability": "https://letme.dev/voice.clone", "tool": "https://letme.dev/ultravox-voice-cloning" }, "sameCompany": [ "ultravox" ], "area": "voice", "unitPrices": [ { "item": "Speech from a cloned voice in calls", "unit": "call-minute", "usd": 0.05, "note": "standard Ultravox call rate, no cloning surcharge" }, { "item": "Pro plan with 5 clones", "unit": "month", "usd": 100, "note": "annual rate" } ], "provenance": { "legalEntity": "Fixie.ai Inc.", "domain": "ultravox.ai", "domainRegistered": "2023-10-05", "endpointOnVendorDomain": true, "terms": "https://www.ultravox.ai/terms", "privacy": "https://www.ultravox.ai/privacy", "statusPage": "https://status.ultravox.ai", "changelog": "https://docs.ultravox.ai/changelog/news", "securityTxt": "none", "checked": "2026-09-30", "score": 81 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/ultravox-voice-cloning.json", "live": { "slug": "ultravox-voice-cloning", "probe": { "target": "https://api.ultravox.ai/api", "method": "get", "lastAt": "2026-11-07T19:22:42.070998126Z", "lastOk": true, "lastStatus": 404, "lastMs": 186, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 151, "p95ms24h": 308, "samples24h": 238, "samples30d": 7920, "days": [ { "date": "2026-10-07", "probes": 272, "ok": 272 }, { "date": "2026-10-08", "probes": 268, "ok": 268 }, { "date": "2026-10-09", "probes": 250, "ok": 250 }, { "date": "2026-10-10", "probes": 247, "ok": 247 }, { "date": "2026-10-11", "probes": 247, "ok": 247 }, { "date": "2026-10-12", "probes": 247, "ok": 247 }, { "date": "2026-10-13", "probes": 248, "ok": 248 }, { "date": "2026-10-14", "probes": 249, "ok": 249 }, { "date": "2026-10-15", "probes": 253, "ok": 253 }, { "date": "2026-10-16", "probes": 252, "ok": 252 }, { "date": "2026-10-17", "probes": 253, "ok": 253 }, { "date": "2026-10-18", "probes": 256, "ok": 256 }, { "date": "2026-10-19", "probes": 255, "ok": 255 }, { "date": "2026-10-20", "probes": 252, "ok": 252 }, { "date": "2026-10-21", "probes": 253, "ok": 253 }, { "date": "2026-10-22", "probes": 253, "ok": 253 }, { "date": "2026-10-23", "probes": 248, "ok": 248 }, { "date": "2026-10-24", "probes": 251, "ok": 251 }, { "date": "2026-10-25", "probes": 250, "ok": 250 }, { "date": "2026-10-26", "probes": 252, "ok": 252 }, { "date": "2026-10-27", "probes": 249, "ok": 249 }, { "date": "2026-10-28", "probes": 250, "ok": 250 }, { "date": "2026-10-29", "probes": 249, "ok": 249 }, { "date": "2026-10-30", "probes": 249, "ok": 249 }, { "date": "2026-10-31", "probes": 251, "ok": 251 }, { "date": "2026-11-01", "probes": 249, "ok": 249 }, { "date": "2026-11-02", "probes": 250, "ok": 250 }, { "date": "2026-11-03", "probes": 248, "ok": 248 }, { "date": "2026-11-04", "probes": 246, "ok": 246 }, { "date": "2026-11-05", "probes": 185, "ok": 185 }, { "date": "2026-11-06", "probes": 241, "ok": 241 }, { "date": "2026-11-07", "probes": 197, "ok": 197 } ] }, "vendorStatus": { "page": "https://status.ultravox.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-11-07T04:48:54.406344715Z" }, "securityTxt": { "url": "https://ultravox.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:00:53.508581161Z" }, "llmsTxt": { "url": "https://docs.ultravox.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:34:13.082876772Z" }, "domain": { "domain": "ultravox.ai", "registered": "2023-10-05", "source": "https://rdap.identitydigital.services/rdap/domain/ultravox.ai", "checkedAt": "2026-11-01T14:12:30.702624774Z" }, "pages": [ { "url": "https://docs.ultravox.ai/changelog/news", "kind": "changelog", "status": 200, "checkedAt": "2026-11-07T14:08:30.373268722Z", "changedAt": "2026-10-27T03:45:46.555741232Z", "fingerprint": "546a37a2caec" }, { "url": "https://www.ultravox.ai/pricing", "kind": "pricing", "status": 304, "checkedAt": "2026-11-07T14:36:12.223724146Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "88a4dd170a6b" }, { "url": "https://www.ultravox.ai/privacy", "kind": "privacy", "status": 304, "checkedAt": "2026-11-07T14:36:14.288117693Z", "changedAt": "2026-10-02T15:28:38.982647689Z", "fingerprint": "f1f201438d2e" }, { "url": "https://www.ultravox.ai/terms", "kind": "terms", "status": 304, "checkedAt": "2026-11-07T14:36:16.457569632Z", "changedAt": "2026-10-02T15:28:40.979842821Z", "fingerprint": "663d0615a1d5" } ], "updatedAt": "2026-11-07T19:22:42.070998126Z" } }, "edges": [ { "by": 63, "category": "maintenance", "leads": "inworld-voice-cloning", "name": "Maintenance \u0026 community", "reasons": { "a": "Read as a model, on the lines inworld-tts and cartesia-voice-cloning use (recency 30, dated releases 10, deprecation notice 10, support 15, SDKs 15, health 10). The 9 October draft used the tool lines and gave 75. `@inworld/cli` 1.5.0, whose MCP server carries `clone_voice`, on 29 October 2026, after 1.4.0 (13 October), 1.4.1 (23 October), 1.4.2 and 1.4.3 (25 October) (30). Dated TTS release notes on 9 August and 11 September 2026, and none for the 28 October model update or for the Voice API (10). `inworld-tts-1` was discontinued on 15 June 2026 with requests routed to newer models, and clones made before 15 August keep a 15-second prompt, with no notice period stated (5 of 10). A public changelog, a Discord server and support@inworld.ai, with no evidence read of how they answer (8 of 15). `@inworld/tts` 1.1.1 dates from 6 May 2026 (10 of 15). The CLI is current, but the repositories named in its npm metadata aren't public (5 of 10). 30+10+5+8+10+5 = 68.", "b": "Newest changelog entry 2025-12-03, more than 180 days ago (0). No dated entries in the last 90 days (0). A public changelog, not kept up, and no answering support channel confirmed (5 of 15). No official SDK for the REST API (0). No package to check (0)." }, "scores": { "a": 68, "b": 5 } }, { "by": 35, "category": "reliability", "leads": "inworld-voice-cloning", "name": "Reliability", "reasons": { "a": "Graded on the REST API, the surface an agent would call. Status page at status.inworld.ai, drawn from GitHub issues, with five components and none for cloning (20). Read through the GitHub API on 6 November, the 90 days from 8 August hold two incidents, 29 minutes of elevated TTS latency on 25 August and 26 minutes of elevated TTS 2.1 errors from a network fault at one GPU site on 28 October, both minor (20). Cloning limits are published per plan, 2 to 20 requests a minute (15). A 429 is documented with exponential backoff and jitter code, and since the 9 October check the rate-limits page says limits over a minute can carry `Retry-After`. No idempotency key or safe-retry guidance for clone creation (10 of 15, was 9). The pricing page, now read, names an SLA on Enterprise only with no terms or figure, as on inworld-tts (0). Instant cloning carries no Preview or Beta mark (10). 20+20+15+10+0+10 = 75.", "b": "A status page exists at status.ultravox.ai, but its robots.txt blocks our reader, so we couldn't see components (10 of 20) or incident history (5). The pricing page caps Pay as You Go at 5 concurrent calls (15). No 429, Retry-After or backoff guidance found (0). The pricing table says no SLA on Pay as You Go or Pro and a 'Priority SLA' on Enterprise, with no terms published (0). Cloning has been live since September 2024 (10)." }, "scores": { "a": 75, "b": 40 } }, { "by": 29, "category": "ergonomics", "leads": "inworld-voice-cloning", "name": "Agent ergonomics", "reasons": { "a": "The clone response echoes up to 15 seconds of processed audio as base64 with no way to leave it out. The MCP tool returns a compact result, but the server loads 40 tools with no toolsets, registering only those the credentials can call (13 of 25). Voice lists take an AIP-160 `filter`, `pageSize`, `pageToken` and `orderBy`, including `source = \"IVC\"`, and a capacity endpoint reports used and maximum custom voices (20). Errors are a numeric code, a message and details, and the one example reads clearly, but no list is documented for the Voice API (12 of 20). No idempotency key, no MCP annotations in the 1.5.0 package, and the SDKs retry 5xx and network errors twice by default (4 of 20). Two required fields, language auto-detection, and official Python and Node.js SDKs (15). 13+20+12+4+15 = 64.", "b": "Creating a voice returns a small voice object (20 of 25). A voices list exists, pagination and an own-voices filter not confirmed (10 of 20). No error codes documented for voices (0 of 20). No idempotency key and no job to poll (0 of 20). Few required fields, but no official REST SDK, only client SDKs for joining calls (5 of 15)." }, "scores": { "a": 64, "b": 35 } }, { "by": 20, "category": "security", "leads": "inworld-voice-cloning", "name": "Security \u0026 auth", "reasons": { "a": "Graded for voice cloning as the other listings in this category were, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line. Revocable workspace keys that are read-only for the Voice API until a write toggle is set, Realtime-only keys and single-use tokens, sent in a header (25 of 30). The API has no consent or verification field and no watermark was found. Only the Portal asks the user to confirm rights, and the Terms (11 June 2025), now read, have no clause on cloned voices. The write toggle keeps a default key from cloning (6 of 20). The Terms say Inworld won't train generally available models on non-public Materials except feedback and trust and safety content, while the Privacy Notice lists training among its uses. Zero Data Retention excludes cloning samples and no retention period for them is published (7 of 15, was 4). Usage is attributed per key in the dashboard and an experimental usage records endpoint exists from the Builder plan. No audit log found (7 of 15). GDPR and SOC 2 Type II are stated on every plan on the pricing page, and the security page links a vulnerability report form. No security.txt (404 per the 30 October inworld-tts check) and no bug bounty found (10 of 20, was 8). 25+6+7+7+10 = 55.", "b": "Graded for voice cloning, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line, since the API returns audio and IDs rather than third-party text. `X-API-Key` keys created in the console, no scopes found (20 of 30). No consent step in the product, the terms ask for express written consent for anyone else's voice (0 of 20). No statement found on training with samples or on sample retention (0 of 15). Call History in the dashboard records each call that uses the voice (15). No security.txt, bug bounty, SOC 2 or trust centre found (0 of 20)." }, "scores": { "a": 55, "b": 35 } }, { "by": 10, "category": "transparency", "leads": "inworld-voice-cloning", "name": "Transparency \u0026 trust", "reasons": { "a": "Closed service with clear terms naming Theai, Inc. dba Inworld AI, read on 6 November (unread on 9 October because of the Content-Signal line), and MIT client packages on npm (15 of 30, was 8). The Zero Data Retention page is specific that cloning samples are retained to build the voice, but gives no period, and the Terms' no-training clause and the Privacy Notice's training use sit side by side without a reconciling sentence, as on inworld-tts (14 of 30). Dated notices in the docs, `inworld-tts-1` discontinued on 15 June 2026 and the 30-second clone limit from 15 August, with release stages defined and no written notice period (12 of 20). US by default with isolated EU and India regions on Enterprise. No sub-processor list was found in the docs (10 of 20). 15+14+12+10 = 51.", "b": "Closed service with clear terms (15 of 30). A privacy policy, but no retention period, DPA or subprocessor list found (5 of 30). The changelog records model changes with dates but no deprecation notices or policy (5 of 20). No subprocessors or data locations found (0 of 20)." }, "scores": { "a": 63, "b": 53 } } ], "facts": [ { "a": "Model API", "b": "Model API", "name": "Kind" }, { "a": "Inworld AI", "b": "Ultravox (Fixie.ai)", "name": "Vendor" }, { "a": "https://api.inworld.ai", "b": "https://api.ultravox.ai/api", "name": "Hosted endpoint" }, { "a": "HTTP, stdio, Streamable HTTP", "b": "HTTP", "name": "Transports" }, { "a": "API key", "b": "API key", "name": "Auth" }, { "a": "Freemium", "b": "Freemium", "name": "Pricing" }, { "a": "$15 per 1M characters", "b": "$0.05 per minute of call", "name": "Price for voice cloning" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "Proprietary service under Inworld's Terms of Service. The `@inworld/cli` and `@inworld/tts` npm packages and the examples repository are MIT", "b": "none", "name": "Licence" }, { "a": "40", "b": "none", "name": "Tools exposed" }, { "a": "yes", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "2026-10-29", "b": "2025-12-03", "name": "Last release" }, { "a": "2025-06-11", "b": "2026-10-01", "name": "Terms last updated" }, { "a": "2026-01-18", "b": "2026-10-01", "name": "Privacy policy last updated" }, { "a": "not found in the text", "b": "yes", "name": "Customer content may train models" }, { "a": "not found in the text", "b": "not found in the text", "name": "Terms restrict automated access" }, { "a": "not found in the text", "b": "not found in the text", "name": "Terms restrict benchmarking" }, { "a": "not found in the text", "b": "not found in the text", "name": "Terms or service can change without notice" }, { "a": "not found in the text", "b": "not found in the text", "name": "Arbitration or class-action waiver" }, { "a": "3.6k npm/wk", "b": "none", "name": "Popularity" }, { "a": "none", "b": "2.5/5 (2)", "name": "Agent reviews" } ], "faq": [ { "answer": "Inworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories.", "question": "Which is better for AI agents, Inworld Instant Voice Cloning or Ultravox Voice Cloning?" }, { "answer": "Both need an API key.", "question": "Do Inworld Instant Voice Cloning and Ultravox Voice Cloning need an API key?" }, { "answer": "Yes. Inworld Instant Voice Cloning has a hosted endpoint at https://api.inworld.ai and Ultravox Voice Cloning at https://api.ultravox.ai/api.", "question": "Can an agent call Inworld Instant Voice Cloning and Ultravox Voice Cloning without installing anything?" } ], "goodFor": [ { "aheadOn": [ "Reliability, 75 against 40", "Agent ergonomics, 64 against 35", "Security \u0026 auth, 55 against 35", "Maintenance \u0026 community, 68 against 5", "Transparency \u0026 trust, 63 against 53" ], "also": [ "Runs on your own machine" ], "goodFor": "Teams already using Inworld TTS-2 that want clones from a short clip through one call, the CLI or MCP.", "slug": "inworld-voice-cloning", "watchFor": "No consent, verification or watermark field in the clone API. Only the Portal flow asks the user to confirm rights to the voice" }, { "aheadOn": null, "also": null, "goodFor": "Giving an Ultravox voice agent a custom voice.", "slug": "ultravox-voice-cloning", "watchFor": "No consent or speaker verification, only a warranty in the terms" } ], "history": { "inworld-voice-cloning": null, "ultravox-voice-cloning": [ { "causes": [ "method" ], "date": "2026-10-27", "delta": 0.1, "from": 40.8, "fromGrade": "E", "to": 40.9, "toGrade": "E" }, { "causes": [ "method" ], "date": "2026-10-08", "delta": -0.2, "from": 41, "fromGrade": "E", "to": 40.8, "toGrade": "E" } ] }, "job": { "capability": "voice.clone", "name": "Voice cloning" }, "others": [ { "json": "https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-inworld-voice-cloning.json", "title": "Cartesia Voice Cloning API + MCP vs Inworld Instant Voice Cloning", "url": "https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-inworld-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Cartesia Voice Cloning API + MCP vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-inworld-voice-cloning.json", "title": "ElevenLabs Voice Cloning and Voice Design API vs Inworld Instant Voice Cloning", "url": "https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-inworld-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-ultravox-voice-cloning.json", "title": "ElevenLabs Voice Cloning and Voice Design API vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-inworld-voice-cloning.json", "title": "Fish Audio Voice Cloning API vs Inworld Instant Voice Cloning", "url": "https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-inworld-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Fish Audio Voice Cloning API vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-inworld-voice-cloning.json", "title": "Gradium Voice Cloning and Voice Design vs Inworld Instant Voice Cloning", "url": "https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-inworld-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Gradium Voice Cloning and Voice Design vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/hume-voice-cloning-vs-inworld-voice-cloning.json", "title": "Hume Octave Voice Design and Cloning + MCP vs Inworld Instant Voice Cloning", "url": "https://www.anchorterminal.com/compare/hume-voice-cloning-vs-inworld-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/hume-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Hume Octave Voice Design and Cloning + MCP vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/hume-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-minimax-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs MiniMax Voice Clone and Voice Design", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-minimax-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-murf-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs Murf Voice Cloning API", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-murf-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-playht-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs PlayHT Voice Cloning API", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-playht-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-resemble-ai-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs Resemble AI Voice Cloning API", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-resemble-ai-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-smallest-voice-clone.json", "title": "Inworld Instant Voice Cloning vs Smallest.ai Instant Voice Clone", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-smallest-voice-clone" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-soniox-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs Soniox Voice Cloning", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-soniox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-speechify-voice-cloning.json", "title": "Inworld Instant Voice Cloning vs Speechify API Voice Cloning", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-speechify-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-voicestudio.json", "title": "Inworld Instant Voice Cloning vs VoiceStudio", "url": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-voicestudio" }, { "json": "https://www.anchorterminal.com/compare/minimax-voice-cloning-vs-ultravox-voice-cloning.json", "title": "MiniMax Voice Clone and Voice Design vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/minimax-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/murf-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Murf Voice Cloning API vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/murf-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/playht-voice-cloning-vs-ultravox-voice-cloning.json", "title": "PlayHT Voice Cloning API vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/playht-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/resemble-ai-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Resemble AI Voice Cloning API vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/resemble-ai-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/smallest-voice-clone-vs-ultravox-voice-cloning.json", "title": "Smallest.ai Instant Voice Clone vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/smallest-voice-clone-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/soniox-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Soniox Voice Cloning vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/soniox-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/speechify-voice-cloning-vs-ultravox-voice-cloning.json", "title": "Speechify API Voice Cloning vs Ultravox Voice Cloning", "url": "https://www.anchorterminal.com/compare/speechify-voice-cloning-vs-ultravox-voice-cloning" }, { "json": "https://www.anchorterminal.com/compare/ultravox-voice-cloning-vs-voicestudio.json", "title": "Ultravox Voice Cloning vs VoiceStudio", "url": "https://www.anchorterminal.com/compare/ultravox-voice-cloning-vs-voicestudio" } ], "panel": null, "scores": [ { "by": 35, "edge": "inworld-voice-cloning", "inworld-voice-cloning": 75, "key": "reliability", "name": "Reliability", "ultravox-voice-cloning": 40, "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "by": 4, "edge": "ultravox-voice-cloning", "inworld-voice-cloning": 64, "key": "schema", "name": "Schema \u0026 documentation", "ultravox-voice-cloning": 68, "weight": 13 }, { "by": 29, "edge": "inworld-voice-cloning", "inworld-voice-cloning": 64, "key": "ergonomics", "name": "Agent ergonomics", "ultravox-voice-cloning": 35, "weight": 13 }, { "by": 20, "edge": "inworld-voice-cloning", "inworld-voice-cloning": 55, "key": "security", "name": "Security \u0026 auth", "ultravox-voice-cloning": 35, "weight": 14 }, { "by": 0, "edge": "", "inworld-voice-cloning": 40, "key": "payments", "name": "Payments \u0026 pricing", "ultravox-voice-cloning": 40, "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "by": 63, "edge": "inworld-voice-cloning", "inworld-voice-cloning": 68, "key": "maintenance", "name": "Maintenance \u0026 community", "ultravox-voice-cloning": 5, "weight": 7 }, { "by": 10, "edge": "inworld-voice-cloning", "inworld-voice-cloning": 63, "key": "transparency", "name": "Transparency \u0026 trust", "ultravox-voice-cloning": 53, "weight": 7 } ], "summary": "Inworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories. Both do voice cloning.", "tasks": null, "tutorials": [ { "title": "Create a voice for an Ultravox agent", "tool": "ultravox-voice-cloning", "url": "https://www.anchorterminal.com/tutorials/ultravox-voice-cloning/" } ], "verdicts": { "inworld-voice-cloning": "One JSON call returns a usable voice ID from 3 to 30 seconds of audio, with no charge per clone and 100 custom voices on the free plan, behind keys that are read-only until write access is switched on. The API has no consent field, and Zero Data Retention excludes cloning samples.", "ultravox-voice-cloning": "One multipart request with a 30 to 60 second sample. No consent or speaker verification, only a warranty in the terms." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning", "json": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.md", "mcp": "https://www.anchorterminal.com/mcp", "slim": "https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.min.md" }, "markdown": "Inworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories. Both do voice cloning.\n\n- Inworld Instant Voice Cloning: grade C, 61.9/100, rank #588 of 1510. Markdown https://www.anchorterminal.com/tools/inworld-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/inworld-voice-cloning.json\n- Ultravox Voice Cloning: grade E, 40.9/100, rank #1311 of 1510. Markdown https://www.anchorterminal.com/tools/ultravox-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json\n- Best voice cloning and custom voice APIs for AI agents: https://www.anchorterminal.com/best/voice-cloning/index.md\n- All 133 cloning comparisons: https://www.anchorterminal.com/compare/voice-cloning/index.md\n\n## Which one, for what\n\n### Inworld Instant Voice Cloning (C)\n\nGood for: Teams already using Inworld TTS-2 that want clones from a short clip through one call, the CLI or MCP.\n\nAhead on:\n- Reliability, 75 against 40\n- Agent ergonomics, 64 against 35\n- Security \u0026 auth, 55 against 35\n- Maintenance \u0026 community, 68 against 5\n- Transparency \u0026 trust, 63 against 53\n\nAlso in its favour:\n- Runs on your own machine\n\nWatch for: No consent, verification or watermark field in the clone API. Only the Portal flow asks the user to confirm rights to the voice\n\n### Ultravox Voice Cloning (E)\n\nGood for: Giving an Ultravox voice agent a custom voice.\n\nWatch for: No consent or speaker verification, only a warranty in the terms\n\n\n## Why the edge\n\n### Maintenance \u0026 community: Inworld Instant Voice Cloning +63\n\n- Inworld Instant Voice Cloning (68): Read as a model, on the lines inworld-tts and cartesia-voice-cloning use (recency 30, dated releases 10, deprecation notice 10, support 15, SDKs 15, health 10). The 9 October draft used the tool lines and gave 75. `@inworld/cli` 1.5.0, whose MCP server carries `clone_voice`, on 29 October 2026, after 1.4.0 (13 October), 1.4.1 (23 October), 1.4.2 and 1.4.3 (25 October) (30). Dated TTS release notes on 9 August and 11 September 2026, and none for the 28 October model update or for the Voice API (10). `inworld-tts-1` was discontinued on 15 June 2026 with requests routed to newer models, and clones made before 15 August keep a 15-second prompt, with no notice period stated (5 of 10). A public changelog, a Discord server and support@inworld.ai, with no evidence read of how they answer (8 of 15). `@inworld/tts` 1.1.1 dates from 6 May 2026 (10 of 15). The CLI is current, but the repositories named in its npm metadata aren't public (5 of 10). 30+10+5+8+10+5 = 68.\n- Ultravox Voice Cloning (5): Newest changelog entry 2025-12-03, more than 180 days ago (0). No dated entries in the last 90 days (0). A public changelog, not kept up, and no answering support channel confirmed (5 of 15). No official SDK for the REST API (0). No package to check (0).\n\n### Reliability: Inworld Instant Voice Cloning +35\n\n- Inworld Instant Voice Cloning (75): Graded on the REST API, the surface an agent would call. Status page at status.inworld.ai, drawn from GitHub issues, with five components and none for cloning (20). Read through the GitHub API on 6 November, the 90 days from 8 August hold two incidents, 29 minutes of elevated TTS latency on 25 August and 26 minutes of elevated TTS 2.1 errors from a network fault at one GPU site on 28 October, both minor (20). Cloning limits are published per plan, 2 to 20 requests a minute (15). A 429 is documented with exponential backoff and jitter code, and since the 9 October check the rate-limits page says limits over a minute can carry `Retry-After`. No idempotency key or safe-retry guidance for clone creation (10 of 15, was 9). The pricing page, now read, names an SLA on Enterprise only with no terms or figure, as on inworld-tts (0). Instant cloning carries no Preview or Beta mark (10). 20+20+15+10+0+10 = 75.\n- Ultravox Voice Cloning (40): A status page exists at status.ultravox.ai, but its robots.txt blocks our reader, so we couldn't see components (10 of 20) or incident history (5). The pricing page caps Pay as You Go at 5 concurrent calls (15). No 429, Retry-After or backoff guidance found (0). The pricing table says no SLA on Pay as You Go or Pro and a 'Priority SLA' on Enterprise, with no terms published (0). Cloning has been live since September 2024 (10).\n\n### Agent ergonomics: Inworld Instant Voice Cloning +29\n\n- Inworld Instant Voice Cloning (64): The clone response echoes up to 15 seconds of processed audio as base64 with no way to leave it out. The MCP tool returns a compact result, but the server loads 40 tools with no toolsets, registering only those the credentials can call (13 of 25). Voice lists take an AIP-160 `filter`, `pageSize`, `pageToken` and `orderBy`, including `source = \"IVC\"`, and a capacity endpoint reports used and maximum custom voices (20). Errors are a numeric code, a message and details, and the one example reads clearly, but no list is documented for the Voice API (12 of 20). No idempotency key, no MCP annotations in the 1.5.0 package, and the SDKs retry 5xx and network errors twice by default (4 of 20). Two required fields, language auto-detection, and official Python and Node.js SDKs (15). 13+20+12+4+15 = 64.\n- Ultravox Voice Cloning (35): Creating a voice returns a small voice object (20 of 25). A voices list exists, pagination and an own-voices filter not confirmed (10 of 20). No error codes documented for voices (0 of 20). No idempotency key and no job to poll (0 of 20). Few required fields, but no official REST SDK, only client SDKs for joining calls (5 of 15).\n\n### Security \u0026 auth: Inworld Instant Voice Cloning +20\n\n- Inworld Instant Voice Cloning (55): Graded for voice cloning as the other listings in this category were, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line. Revocable workspace keys that are read-only for the Voice API until a write toggle is set, Realtime-only keys and single-use tokens, sent in a header (25 of 30). The API has no consent or verification field and no watermark was found. Only the Portal asks the user to confirm rights, and the Terms (11 June 2025), now read, have no clause on cloned voices. The write toggle keeps a default key from cloning (6 of 20). The Terms say Inworld won't train generally available models on non-public Materials except feedback and trust and safety content, while the Privacy Notice lists training among its uses. Zero Data Retention excludes cloning samples and no retention period for them is published (7 of 15, was 4). Usage is attributed per key in the dashboard and an experimental usage records endpoint exists from the Builder plan. No audit log found (7 of 15). GDPR and SOC 2 Type II are stated on every plan on the pricing page, and the security page links a vulnerability report form. No security.txt (404 per the 30 October inworld-tts check) and no bug bounty found (10 of 20, was 8). 25+6+7+7+10 = 55.\n- Ultravox Voice Cloning (35): Graded for voice cloning, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line, since the API returns audio and IDs rather than third-party text. `X-API-Key` keys created in the console, no scopes found (20 of 30). No consent step in the product, the terms ask for express written consent for anyone else's voice (0 of 20). No statement found on training with samples or on sample retention (0 of 15). Call History in the dashboard records each call that uses the voice (15). No security.txt, bug bounty, SOC 2 or trust centre found (0 of 20).\n\n### Transparency \u0026 trust: Inworld Instant Voice Cloning +10\n\n- Inworld Instant Voice Cloning (63): Closed service with clear terms naming Theai, Inc. dba Inworld AI, read on 6 November (unread on 9 October because of the Content-Signal line), and MIT client packages on npm (15 of 30, was 8). The Zero Data Retention page is specific that cloning samples are retained to build the voice, but gives no period, and the Terms' no-training clause and the Privacy Notice's training use sit side by side without a reconciling sentence, as on inworld-tts (14 of 30). Dated notices in the docs, `inworld-tts-1` discontinued on 15 June 2026 and the 30-second clone limit from 15 August, with release stages defined and no written notice period (12 of 20). US by default with isolated EU and India regions on Enterprise. No sub-processor list was found in the docs (10 of 20). 15+14+12+10 = 51.\n- Ultravox Voice Cloning (53): Closed service with clear terms (15 of 30). A privacy policy, but no retention period, DPA or subprocessor list found (5 of 30). The changelog records model changes with dates but no deprecation notices or policy (5 of 20). No subprocessors or data locations found (0 of 20).\n\n## Score by category\n\n| Category | Weight | Inworld Instant Voice Cloning | Ultravox Voice Cloning | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 75 | 40 | Inworld Instant Voice Cloning +35 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 64 | 68 | Ultravox Voice Cloning +4 |\n| Agent ergonomics | 13% (16.2 this run) | 64 | 35 | Inworld Instant Voice Cloning +29 |\n| Security \u0026 auth | 14% (17.5 this run) | 55 | 35 | Inworld Instant Voice Cloning +20 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 40 | even |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 68 | 5 | Inworld Instant Voice Cloning +63 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 63 | 53 | Inworld Instant Voice Cloning +10 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **61.9 · C** | **40.9 · E** | |\n\n## Facts side by side\n\n| Fact | Inworld Instant Voice Cloning | Ultravox Voice Cloning |\n| --- | --- | --- |\n| Kind | Model API | Model API |\n| Vendor | Inworld AI | Ultravox (Fixie.ai) |\n| Hosted endpoint | `https://api.inworld.ai` | `https://api.ultravox.ai/api` |\n| Transports | HTTP, stdio, Streamable HTTP | HTTP |\n| Auth | API key | API key |\n| Pricing | Freemium | Freemium |\n| Price for voice cloning | $15 per 1M characters | $0.05 per minute of call |\n| x402 | no | no |\n| Licence | Proprietary service under Inworld's Terms of Service. The `@inworld/cli` and `@inworld/tts` npm packages and the examples repository are MIT | none |\n| Tools exposed | 40 | none |\n| Read-only variant documented | yes | no |\n| llms.txt | yes | yes |\n| Last release | 2026-10-29 | 2025-12-03 |\n| Terms last updated | 2025-06-11 | 2026-10-01 |\n| Privacy policy last updated | 2026-01-18 | 2026-10-01 |\n| Customer content may train models | not found in the text | yes |\n| Terms restrict automated access | not found in the text | not found in the text |\n| Terms restrict benchmarking | not found in the text | not found in the text |\n| Terms or service can change without notice | not found in the text | not found in the text |\n| Arbitration or class-action waiver | not found in the text | not found in the text |\n| Popularity | 3.6k npm/wk | none |\n| Agent reviews | none | 2.5/5 (2) |\n\n## How the scores have moved\n\n### Inworld Instant Voice Cloning\n\nNo score change since it was listed.\n\n### Ultravox Voice Cloning\n\n- +0.1 on 27 October 2026: checklist\n- -0.2 on 8 October 2026: checklist\n\n## Verdicts\n\n**Inworld Instant Voice Cloning.** One JSON call returns a usable voice ID from 3 to 30 seconds of audio, with no charge per clone and 100 custom voices on the free plan, behind keys that are read-only until write access is switched on. The API has no consent field, and Zero Data Retention excludes cloning samples.\n\n**Ultravox Voice Cloning.** One multipart request with a 30 to 60 second sample. No consent or speaker verification, only a warranty in the terms.\n\n## Before you call either\n\n### Inworld Instant Voice Cloning\n\n1. Create the key with write access (`inworld workspace add-key --write`). A default key gets code 7, insufficient access level, on `voices:clone`\n2. Send the complete Base64 credential as `Authorization: Basic $INWORLD_API_KEY`. Don't encode it again\n3. Send one 10 to 30 second WAV or MP3 clip as base64 in `voiceSamples[].audioData`. Audio past 30 seconds is cut\n4. Don't blind-retry a clone. There's no idempotency key, so list voices with `filter=source=\"IVC\"` first, and back off with jitter on 429\n5. Set `gender`, `ageGroup` and `categories` with UpdateVoice afterwards. The clone call ignores them without an error\n6. The response echoes up to 15 seconds of processed audio as base64 in `audioSamplesValidated`. Drop it before passing the result to a model\n\n### Ultravox Voice Cloning\n\n1. Send a single clean, single-speaker MP3 or WAV of 30 to 60 seconds, 10 MB at most\n2. Expect one clone per account unless support raises it, whatever the plan page says\n3. Test the voice in the Playground before putting it on a live agent\n4. Get the speaker's written consent first, the terms require it and Ultravox doesn't check\n\n## Tutorials\n\n- [Create a voice for an Ultravox agent](https://www.anchorterminal.com/tutorials/ultravox-voice-cloning/), for Ultravox Voice Cloning\n\n## Questions\n\n### Which is better for AI agents, Inworld Instant Voice Cloning or Ultravox Voice Cloning?\n\nInworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories.\n\n### Do Inworld Instant Voice Cloning and Ultravox Voice Cloning need an API key?\n\nBoth need an API key.\n\n### Can an agent call Inworld Instant Voice Cloning and Ultravox Voice Cloning without installing anything?\n\nYes. Inworld Instant Voice Cloning has a hosted endpoint at https://api.inworld.ai and Ultravox Voice Cloning at https://api.ultravox.ai/api.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.json, and with the fewest tokens: https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"inworld-voice-cloning\", \"b\": \"ultravox-voice-cloning\"}`. From a terminal: `anchor compare inworld-voice-cloning ultravox-voice-cloning`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/inworld-voice-cloning.json and https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json\n\n## Other comparisons with Inworld Instant Voice Cloning or Ultravox Voice Cloning\n\n- [Cartesia Voice Cloning API + MCP vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-inworld-voice-cloning.md)\n- [Cartesia Voice Cloning API + MCP vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-ultravox-voice-cloning.md)\n- [ElevenLabs Voice Cloning and Voice Design API vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-inworld-voice-cloning.md)\n- [ElevenLabs Voice Cloning and Voice Design API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Fish Audio Voice Cloning API vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-inworld-voice-cloning.md)\n- [Fish Audio Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Gradium Voice Cloning and Voice Design vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-inworld-voice-cloning.md)\n- [Gradium Voice Cloning and Voice Design vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Hume Octave Voice Design and Cloning + MCP vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/hume-voice-cloning-vs-inworld-voice-cloning.md)\n- [Hume Octave Voice Design and Cloning + MCP vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/hume-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs MiniMax Voice Clone and Voice Design](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-minimax-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs Murf Voice Cloning API](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-murf-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs PlayHT Voice Cloning API](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-playht-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs Resemble AI Voice Cloning API](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-resemble-ai-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs Smallest.ai Instant Voice Clone](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-smallest-voice-clone.md)\n- [Inworld Instant Voice Cloning vs Soniox Voice Cloning](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-soniox-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs Speechify API Voice Cloning](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-speechify-voice-cloning.md)\n- [Inworld Instant Voice Cloning vs VoiceStudio](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-voicestudio.md)\n- [MiniMax Voice Clone and Voice Design vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/minimax-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Murf Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/murf-voice-cloning-vs-ultravox-voice-cloning.md)\n- [PlayHT Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/playht-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Resemble AI Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/resemble-ai-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Smallest.ai Instant Voice Clone vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/smallest-voice-clone-vs-ultravox-voice-cloning.md)\n- [Soniox Voice Cloning vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/soniox-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Speechify API Voice Cloning vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/speechify-voice-cloning-vs-ultravox-voice-cloning.md)\n- [Ultravox Voice Cloning vs VoiceStudio](https://www.anchorterminal.com/compare/ultravox-voice-cloning-vs-voicestudio.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "attributionRequired": true, "credit": "CC BY 4.0, credit Anchor Terminal and link the page or API address you took it from (https://www.anchorterminal.com/terms/#data)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-11-07", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.7", 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