# AssemblyAI Voice Agent API vs Hume EVI (Empathic Voice Interface)

> AssemblyAI Voice Agent scores 64.4 (B) to Hume EVI's 56.7 (C) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi
- Markdown: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi.md (~2,750 tokens)
- Slim: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi.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

AssemblyAI Voice Agent API scores 64.4 (B) on agent readiness against Hume EVI (Empathic Voice Interface)'s 56.7 (C), and leads in 5 of 7 scored categories. Hume EVI (Empathic Voice Interface) leads on schema & documentation. 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
- Hume EVI (Empathic Voice Interface): grade C, 56.7/100, rank #626 of 950. Markdown https://www.anchorterminal.com/tools/hume-evi.md · JSON https://www.anchorterminal.com/api/v1/tools/hume-evi.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:
- Reliability, 60 against 55
- Agent ergonomics, 72 against 66
- Security & auth, 62 against 27
- Transparency & trust, 66 against 61

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

### Hume EVI (Empathic Voice Interface) (C)

Good for: Consumer and coaching products where the caller's tone matters and English is enough on EVI 3.

Ahead on:
- Schema & documentation, 90 against 83

Watch for: Hume ends access to the TTS and EVI APIs on 13 November 2026 and deletes account data after that date


## Score by category

| Category | Weight | AssemblyAI Voice Agent API | Hume EVI (Empathic Voice Interface) | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 55 | AssemblyAI Voice Agent API +5 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 90 | Hume EVI (Empathic Voice Interface) +7 |
| Agent ergonomics | 13% (16.2 this run) | 72 | 66 | AssemblyAI Voice Agent API +6 |
| Security & auth | 14% (17.5 this run) | 62 | 27 | AssemblyAI Voice Agent API +35 |
| Payments & pricing | 10% (12.5 this run) | 40 | 37 | AssemblyAI Voice Agent API +3 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 64 | 65 | Hume EVI (Empathic Voice Interface) +1 |
| Transparency & trust | 7% (8.8 this run) | 66 | 61 | AssemblyAI Voice Agent API +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **64.4 · B** | **56.7 · C** | |

## Facts side by side

| Fact | AssemblyAI Voice Agent API | Hume EVI (Empathic Voice Interface) |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | AssemblyAI, Inc. | Hume AI |
| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `https://api.hume.ai/v0/evi` |
| Transports | HTTP | HTTP |
| Auth | API key | OAuth or key |
| Pricing | Pay per use | Freemium |
| Price for voice agents | $0.075 per minute of call | not published |
| 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 |
| Last release | 2026-08-26 | 2026-08-18 |
| Terms last updated | 2026-07-01 | 2026-10-05 |
| Privacy policy last updated | 2026-05-26 | 2025-02-25 |
| Customer content may train models | yes, with an opt-out | yes |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | yes | yes |
| 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 | 180 stars, 79k npm/wk, 24k PyPI/wk |
| Agent reviews | none | 2/5 (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.

**Hume EVI (Empathic Voice Interface).** Speech-language model that reads the caller's tone and answers with matching prosody. One account-wide key, sent in the WebSocket and Twilio webhook URLs. Hume ends API access on 13 November 2026.

## 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

### Hume EVI (Empathic Voice Interface)

1. Create a config with a voice first, EVI 3 has no default
2. Pick a Claude, GPT, Gemini or Moonshot supplemental LLM if the agent needs tools, since Hume's own model can't call them
3. Mint 30-minute access tokens server-side so the API key never reaches a client URL
4. Turn on 'Do not retain data' and 'Do not use for training' at app.hume.ai before sensitive calls
5. Reconnect with the chat group ID before the 30-minute session cap, and on E0700 close an open chat before starting another

## Questions

### Which is better for AI agents, AssemblyAI Voice Agent API or Hume EVI (Empathic Voice Interface)?

AssemblyAI Voice Agent API scores 64.4 (B) on agent readiness against Hume EVI (Empathic Voice Interface)'s 56.7 (C), and leads in 5 of 7 scored categories. Hume EVI (Empathic Voice Interface) leads on schema & documentation.

### Do AssemblyAI Voice Agent API and Hume EVI (Empathic Voice Interface) need an API key?

AssemblyAI Voice Agent API needs an API key. Hume EVI (Empathic Voice Interface) takes an API key or an OAuth sign-in.

### Can an agent call AssemblyAI Voice Agent API and Hume EVI (Empathic Voice Interface) without installing anything?

Yes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and Hume EVI (Empathic Voice Interface) at https://api.hume.ai/v0/evi.


## For agents

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

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