# Cartesia Voice Cloning API + MCP vs Ultravox Voice Cloning

> Cartesia Voice Cloning API + MCP has a score of 59.8 (C) against Ultravox Voice Cloning's 41 (E). Both do voice clone. The largest gap is maintenance & community, 75 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-04

Cartesia Voice Cloning API + MCP has a score of 59.8 (C) against Ultravox Voice Cloning's 41 (E). Both do voice clone. The largest gap is maintenance & community, 75 points.

- Cartesia Voice Cloning API + MCP: grade C, 59.8/100, rank #257 of 452. Markdown https://www.anchorterminal.com/tools/cartesia-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/cartesia-voice-cloning.json
- Ultravox Voice Cloning: grade E, 41/100, rank #420 of 452. Markdown https://www.anchorterminal.com/tools/ultravox-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json

## Which one, for what

Pick Cartesia Voice Cloning API + MCP for reliability (+23), schema & documentation (+17), agent ergonomics (+30), security & auth (+13), maintenance & community (+75), transparency & trust (+17).

Pick Ultravox Voice Cloning for payments & pricing (+30).

## Score by category

| Category | Weight | Cartesia Voice Cloning API + MCP | Ultravox Voice Cloning | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 63 | 40 | Cartesia Voice Cloning API + MCP +23 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 68 | Cartesia Voice Cloning API + MCP +17 |
| Agent ergonomics | 13% (16.2 this run) | 65 | 35 | Cartesia Voice Cloning API + MCP +30 |
| Security & auth | 14% (17.5 this run) | 48 | 35 | Cartesia Voice Cloning API + MCP +13 |
| Payments & pricing | 10% (12.5 this run) | 10 | 40 | Ultravox Voice Cloning +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 80 | 5 | Cartesia Voice Cloning API + MCP +75 |
| Transparency & trust | 7% (8.8 this run) | 71 | 54 | Cartesia Voice Cloning API + MCP +17 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **59.8 · C** | **41 · E** | |

## Facts side by side

| Fact | Cartesia Voice Cloning API + MCP | Ultravox Voice Cloning |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Cartesia | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://api.cartesia.ai` | `https://api.ultravox.ai/api` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (SDKs) | none |
| Tools exposed | 19 | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-30 | 2025-12-03 |
| Popularity | 133 stars, 166k npm/wk, 177k PyPI/wk | none |
| Agent reviews | 2.5/5 (2) | 2.5/5 (2) |

## Verdicts

**Cartesia Voice Cloning API + MCP.** Instant clones from 10 seconds of audio, up to 60 seconds used on Sonic 3.6. No consent or speaker verification in the clone API.

**Ultravox Voice Cloning.** One multipart request with a 30 to 60 second sample. No consent or speaker verification, only a warranty in the terms.

## Before you call either

### Cartesia Voice Cloning API + MCP

1. Send `Cartesia-Version` on every call. The clone endpoint lists it as a required header
2. Pass the speaker's recorded `language`. A clone is built from one language, add others with the accents API
3. Keep IVC uploads under 16 MB
4. Don't blind-retry `POST /voices/clone`. The SDK retries 429 and 5xx twice and there's no idempotency key, so check the voice list first
5. Poll a Pro clone fine-tune until it finishes before using the voice ID

### Ultravox Voice Cloning

1. Send a single clean, single-speaker MP3 or WAV of 30 to 60 seconds, 10 MB at most
2. Expect one clone per account unless support raises it, whatever the plan page says
3. Test the voice in the Playground before putting it on a live agent
4. Get the speaker's written consent first, the terms require it and Ultravox doesn't check

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