# AssemblyAI Voice Agent API vs Retell AI API + MCP (slim)

> Retell AI scores 69.1 (B) to AssemblyAI Voice Agent's 64.4 (B) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai.md (~2,600 tokens) · this version ~680 tokens · JSON https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai.json · canonical https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-09

Retell AI API + MCP scores 69.1 (B) on agent readiness against AssemblyAI Voice Agent API's 64.4 (B), and leads in 4 of 7 scored categories. AssemblyAI Voice Agent API leads on agent ergonomics. Both do voice agents.

- AssemblyAI Voice Agent API: B 64.4, rank #351 of 950 · https://www.anchorterminal.com/tools/assemblyai-voice-agent.min.md
- Retell AI API + MCP: B 69.1, rank #196 of 950 · https://www.anchorterminal.com/tools/retell-ai.min.md
- AssemblyAI Voice Agent API, good for A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own. Ahead on Agent ergonomics, 72 against 60.
- Retell AI API + MCP, good for Teams that want a self-serve phone agent with clear per-component pricing, scoped keys and a choice of LLM and voice from Retell's menu. Ahead on Schema & documentation, 92 against 83; Security & auth, 76 against 62; Maintenance & community, 85 against 64; Transparency & trust, 76 against 66.

| Category | AssemblyAI Voice Agent API | Retell AI API + MCP |
| --- | --- | --- |
| Reliability (16%) | 60 | 60 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 83 | 92 |
| Agent ergonomics (13%) | 72 | 60 |
| Security & auth (14%) | 62 | 76 |
| Payments & pricing (10%) | 40 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 64 | 85 |
| Transparency & trust (7%) | 66 | 76 |

| Fact (where they differ) | AssemblyAI Voice Agent API | Retell AI API + MCP |
| --- | --- | --- |
| Vendor | AssemblyAI, Inc. | Retell AI |
| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `https://api.retellai.com` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Price for voice agents | $0.075 per minute of call | not published |
| Licence | Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file | Apache-2.0 (SDKs) |
| Last release | 2026-08-26 | 2026-09-14 |
| Terms last updated | 2026-07-01 | 2026-06-01 |
| Privacy policy last updated | 2026-05-26 | 2026-07-20 |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | none | 62 stars, 243k npm/wk |
| Agent reviews | none | 3.5/5 (2) |