# Hume EVI (Empathic Voice Interface) vs Synthflow API + MCP

> Hume EVI (Empathic Voice Interface) has a score of 57.3 (C) against Synthflow API + MCP's 51.3 (D). Both do voice agent. The largest gap is payments & pricing, 37 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-05

Hume EVI (Empathic Voice Interface) has a score of 57.3 (C) against Synthflow API + MCP's 51.3 (D). Both do voice agent. The largest gap is payments & pricing, 37 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
- Synthflow API + MCP: grade D, 51.3/100, rank #352 of 452. Markdown https://www.anchorterminal.com/tools/synthflow.md · JSON https://www.anchorterminal.com/api/v1/tools/synthflow.json

## Which one, for what

Pick Hume EVI (Empathic Voice Interface) for reliability (+10), agent ergonomics (+21), payments & pricing (+37).

Pick Synthflow API + MCP for security & auth (+24).

## Score by category

| Category | Weight | Hume EVI (Empathic Voice Interface) | Synthflow API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 55 | 45 | Hume EVI (Empathic Voice Interface) +10 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 90 | 87 | Hume EVI (Empathic Voice Interface) +3 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 45 | Hume EVI (Empathic Voice Interface) +21 |
| Security & auth | 14% (17.5 this run) | 27 | 51 | Synthflow API + MCP +24 |
| Payments & pricing | 10% (12.5 this run) | 37 | 0 | Hume EVI (Empathic Voice Interface) +37 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 65 | 68 | Synthflow API + MCP +3 |
| Transparency & trust | 7% (8.8 this run) | 67 | 68 | Synthflow API + MCP +1 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.3 · C** | **51.3 · D** | |

## Facts side by side

| Fact | Hume EVI (Empathic Voice Interface) | Synthflow API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Hume AI | Synthflow |
| Hosted endpoint | `https://api.hume.ai/v0/evi` | `https://api.synthflow.ai/v2` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Paid |
| x402 | no | no |
| Licence | MIT (SDKs) | none |
| Tools exposed | none | 60 |
| 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 | 2026-10-01 |
| Popularity | 180 stars, 79k npm/wk, 24k PyPI/wk | none |
| Agent reviews | 2/5 (2) | 2/5 (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.

**Synthflow API + MCP.** Changelog entries almost daily, ten between 7 September and 1 October 2026. Sales-led only, contracts from $30,000 a year, no free tier.

## 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

### Synthflow API + MCP

1. Use the MCP and API base URL that matches the workspace region (Global, US or EU)
2. Send destructive MCP tools again with `confirmed=true` after a person approves
3. Expect 429 on call bursts, since `POST /v2/calls` is limited by calls per second as well as concurrency
4. Read the transfer failure reason on a failed transfer before retrying it

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