# Cartesia Sonic TTS API + MCP vs HeyGen Voice (slim)

> HeyGen Voice scores 71.3 (BB) to Cartesia Sonic TTS's 63.8 (B) for text-to-speech. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/cartesia-tts-vs-heygen-voice.md (~2,500 tokens) · this version ~730 tokens · JSON https://www.anchorterminal.com/compare/cartesia-tts-vs-heygen-voice.json · canonical https://www.anchorterminal.com/compare/cartesia-tts-vs-heygen-voice
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-10

HeyGen Voice scores 71.3 (BB) on agent readiness against Cartesia Sonic TTS API + MCP's 63.8 (B), and leads in 5 of 7 scored categories. Cartesia Sonic TTS API + MCP leads on maintenance & community. Both do text-to-speech.

- Cartesia Sonic TTS API + MCP: B 63.8, rank #375 of 961 · https://www.anchorterminal.com/tools/cartesia-tts.min.md
- HeyGen Voice: BB 71.3, rank #131 of 961 · https://www.anchorterminal.com/tools/heygen-voice.min.md
- Cartesia Sonic TTS API + MCP, good for Real-time voice agents that stream LLM output straight into speech and need stable, pinnable models. Ahead on Maintenance & community, 79 against 65. Also Runs on your own machine.
- HeyGen Voice, good for Speech in a voice cloned from one short recording, for agents that already make HeyGen videos or need a cloned narrator with streaming and timestamps. Ahead on Reliability, 75 against 63; Schema & documentation, 94 against 86; Agent ergonomics, 83 against 65; Security & auth, 69 against 58. Also Agent-ready, a grade of BB or better.

| Category | Cartesia Sonic TTS API + MCP | HeyGen Voice |
| --- | --- | --- |
| Reliability (16%) | 63 | 75 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 86 | 94 |
| Agent ergonomics (13%) | 65 | 83 |
| Security & auth (14%) | 58 | 69 |
| Payments & pricing (10%) | 30 | 30 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 79 | 65 |
| Transparency & trust (7%) | 67 | 69 |

| Fact (where they differ) | Cartesia Sonic TTS API + MCP | HeyGen Voice |
| --- | --- | --- |
| Vendor | Cartesia | HeyGen |
| Hosted endpoint | `https://api.cartesia.ai` | `https://api.heygen.com` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Pay per use |
| Price for text-to-speech | $38 per 1M characters | not published |
| Licence | Apache-2.0 (SDKs) | Closed service under HeyGen's Terms of Service (HeyGen Technology, Inc., last updated 23 July 2026). |
| Tools exposed | 15 | none |
| Last release | 2026-09-30 | none |
| Terms last updated | 2024-06-14 |  |
| Privacy policy last updated | 2024-06-14 |  |
| Customer content may train models | yes, with an opt-out |  |
| Terms restrict automated access | yes |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 133 stars, 166k npm/wk, 177k PyPI/wk | none |
| Agent reviews | 3/5 (2) | none |