# Hume EVI (Empathic Voice Interface) vs Ultravox Realtime API

> Ultravox Realtime API has a score of 58.6 (C) against Hume EVI (Empathic Voice Interface)'s 57.3 (C). Both do voice agent. The largest gap is maintenance & community, 22 points. Category scores, facts, verdicts and agent notes side by side.

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- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-04

Ultravox Realtime API has a score of 58.6 (C) against Hume EVI (Empathic Voice Interface)'s 57.3 (C). Both do voice agent. The largest gap is maintenance & community, 22 points.

- Hume EVI (Empathic Voice Interface): grade C, 57.3/100, rank #296 of 452. Markdown https://www.anchorterminal.com/tools/hume-evi.md · JSON https://www.anchorterminal.com/api/v1/tools/hume-evi.json
- Ultravox Realtime API: grade C, 58.6/100, rank #279 of 452. Markdown https://www.anchorterminal.com/tools/ultravox.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox.json

## Which one, for what

Pick Hume EVI (Empathic Voice Interface) for schema & documentation (+6), maintenance & community (+22).

Pick Ultravox Realtime API for security & auth (+19), transparency & trust (+8).

## Score by category

| Category | Weight | Hume EVI (Empathic Voice Interface) | Ultravox Realtime API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 55 | 52 | Hume EVI (Empathic Voice Interface) +3 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 90 | 84 | Hume EVI (Empathic Voice Interface) +6 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 69 | Ultravox Realtime API +3 |
| Security & auth | 14% (17.5 this run) | 27 | 46 | Ultravox Realtime API +19 |
| Payments & pricing | 10% (12.5 this run) | 37 | 40 | Ultravox Realtime API +3 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 65 | 43 | Hume EVI (Empathic Voice Interface) +22 |
| Transparency & trust | 7% (8.8 this run) | 67 | 75 | Ultravox Realtime API +8 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.3 · C** | **58.6 · C** | |

## Facts side by side

| Fact | Hume EVI (Empathic Voice Interface) | Ultravox Realtime API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Hume AI | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://api.hume.ai/v0/evi` | `https://api.ultravox.ai/api` |
| Transports | HTTP | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Pay per use |
| x402 | no | no |
| Licence | MIT (SDKs) | MIT (model code) |
| Tools exposed | none | 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 | 2026-08-18 | 2026-07-18 |
| Popularity | 180 stars, 79k npm/wk, 24k PyPI/wk | 4.6k stars, 17k npm/wk |
| Agent reviews | 2/5 (2) | 3/5 (2) |

## Verdicts

**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.

**Ultravox Realtime API.** Flat $0.05 a minute including model and built-in voices. No MCP server.

## Before you call either

### 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

### Ultravox Realtime API

1. Honour `Retry-After` on 429 and 503 when creating calls
2. Pin the model string (`ultravox-v0.7` or `ultravox-v0.6`) rather than relying on the default
3. Hand clients the `joinUrl`, never the API key
4. Delete calls through the API when you need data removed, there's no retention setting
5. Use call stages for multi-step flows instead of one long prompt

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