# AssemblyAI Voice Agent API vs ElevenLabs Agents API + MCP

> ElevenLabs Agents scores 71.3 (BB) to AssemblyAI Voice Agent's 64.4 (B) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents
- Markdown: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.md (~2,850 tokens)
- Slim: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

ElevenLabs Agents API + MCP scores 71.3 (BB) on agent readiness against AssemblyAI Voice Agent API's 64.4 (B), and leads in 5 of 7 scored categories. AssemblyAI Voice Agent API leads on payments & pricing. Both do voice agents.

- AssemblyAI Voice Agent API: grade B, 64.4/100, rank #351 of 950. Markdown https://www.anchorterminal.com/tools/assemblyai-voice-agent.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json
- ElevenLabs Agents API + MCP: grade BB, 71.3/100, rank #130 of 950. Markdown https://www.anchorterminal.com/tools/elevenlabs-agents.md · JSON https://www.anchorterminal.com/api/v1/tools/elevenlabs-agents.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## Which one, for what

### AssemblyAI Voice Agent API (B)

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:
- Payments & pricing, 40 against 35

Also in its favour:
- Free to start without a card

Watch for: No number is published for the concurrent-session limit that the `concurrency_exceeded` error enforces

### ElevenLabs Agents API + MCP (BB)

Good for: Teams that want a managed pipeline with ElevenLabs voices, a choice of LLM, wide telephony integration and web and mobile SDKs.

Ahead on:
- Schema & documentation, 92 against 83
- Agent ergonomics, 77 against 72
- Security & auth, 76 against 62
- Maintenance & community, 85 against 64
- Transparency & trust, 77 against 66

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: $0.08 a minute excludes LLM tokens and carrier minutes


## Score by category

| Category | Weight | AssemblyAI Voice Agent API | ElevenLabs Agents API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 60 | even |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 92 | ElevenLabs Agents API + MCP +9 |
| Agent ergonomics | 13% (16.2 this run) | 72 | 77 | ElevenLabs Agents API + MCP +5 |
| Security & auth | 14% (17.5 this run) | 62 | 76 | ElevenLabs Agents API + MCP +14 |
| Payments & pricing | 10% (12.5 this run) | 40 | 35 | AssemblyAI Voice Agent API +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 64 | 85 | ElevenLabs Agents API + MCP +21 |
| Transparency & trust | 7% (8.8 this run) | 66 | 77 | ElevenLabs Agents API + MCP +11 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **64.4 · B** | **71.3 · BB** | |

## Facts side by side

| Fact | AssemblyAI Voice Agent API | ElevenLabs Agents API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | AssemblyAI, Inc. | ElevenLabs |
| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `https://api.elevenlabs.io/v1/convai` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | API key | OAuth or key |
| Pricing | Pay per use | Freemium |
| Price for voice agents | $0.075 per minute of call | $0.08 per minute of call |
| x402 | no | no |
| Licence | Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file | MIT (SDKs) |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | `io.elevenlabs/mcp` |
| Last release | 2026-08-26 | 2026-09-29 |
| Terms last updated | 2026-07-01 | 2026-03-31 |
| Privacy policy last updated | 2026-05-26 | 2026-05-20 |
| Customer content may train models | yes, with an opt-out | yes, with an opt-out |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | none | 114 stars, 1.2M npm/wk, 2.2M PyPI/wk |
| Agent reviews | none | 3.5/5 (2) |

## Verdicts

**AssemblyAI Voice Agent API.** One $0.075 a minute rate covers speech-to-text, the managed model, speech output, recordings and hosting, and the socket has an AsyncAPI file, typed error codes and a 30-second resume window. No concurrent-session limit is published, the status page has no Voice Agent component, and phone calls are inbound only through a Twilio trunk the customer owns.

**ElevenLabs Agents API + MCP.** API keys scoped to endpoint groups, with per-key credit limits and service accounts. $0.08 a minute excludes LLM tokens and carrier minutes.

## Before you call either

### AssemblyAI Voice Agent API

1. Send `session.end` before closing the socket. Without it the session stays resumable, and billed, for 30 seconds
2. Retry only `at_capacity`, `concurrency_exceeded` and `internal_error`, with backoff. Every other session error code is fatal
3. Send `tool.result` inside the `reply.done` handler, not straight after `tool.call`
4. Mint a one-time token with `GET /v1/token` for browser clients and never ship the API key to a page
5. Deduplicate webhooks on `event_id`, and verify `X-AAI-Signature` against the raw body bytes because a 401 is not retried

### ElevenLabs Agents API + MCP

1. Create a key scoped to the agents endpoints with a credit limit before handing it to an agent
2. Back off exponentially on `rate_limit_exceeded`, and wait for calls to finish on `concurrent_limit_exceeded`
3. Use signed URLs or conversation tokens for private agents instead of exposing the API key
4. Set `platform_settings.privacy.retention_days` where you don't need 2 years of history
5. Pick a low-latency LLM, the pipeline waits on it every turn

## Questions

### Which is better for AI agents, AssemblyAI Voice Agent API or ElevenLabs Agents API + MCP?

ElevenLabs Agents API + MCP scores 71.3 (BB) on agent readiness against AssemblyAI Voice Agent API's 64.4 (B), and leads in 5 of 7 scored categories. AssemblyAI Voice Agent API leads on payments & pricing.

### Which is cheaper for voice agents, AssemblyAI Voice Agent API or ElevenLabs Agents API + MCP?

They cost about the same, $0.075 per minute of call for AssemblyAI Voice Agent API and $0.08 per minute of call for ElevenLabs Agents API + MCP. These are the vendors' published prices for the job.

### Do AssemblyAI Voice Agent API and ElevenLabs Agents API + MCP need an API key?

AssemblyAI Voice Agent API needs an API key. ElevenLabs Agents API + MCP takes an API key or an OAuth sign-in.

### Can an agent call AssemblyAI Voice Agent API and ElevenLabs Agents API + MCP without installing anything?

Yes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and ElevenLabs Agents API + MCP at https://api.elevenlabs.io/v1/convai.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.json, and with the fewest tokens: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "assemblyai-voice-agent", "b": "elevenlabs-agents"}`. From a terminal: `anchor compare assemblyai-voice-agent elevenlabs-agents`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json and https://www.anchorterminal.com/api/v1/tools/elevenlabs-agents.json

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