# Deepgram Voice Agent API vs Ultravox Realtime API

> Deepgram Voice Agent API has a score of 68.4 (B) against Ultravox Realtime API's 58.6 (C). Both do voice agent. The largest gap is maintenance & community, 42 points. Category scores, facts, verdicts and agent notes side by side.

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- 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: 2026-10-04

Deepgram Voice Agent API has a score of 68.4 (B) against Ultravox Realtime API's 58.6 (C). Both do voice agent. The largest gap is maintenance & community, 42 points.

- Deepgram Voice Agent API: grade B, 68.4/100, rank #126 of 452. Markdown https://www.anchorterminal.com/tools/deepgram-voice-agent.md · JSON https://www.anchorterminal.com/api/v1/tools/deepgram-voice-agent.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 Deepgram Voice Agent API for schema & documentation (+6), security & auth (+25), maintenance & community (+42), transparency & trust (+5).

Pick Ultravox Realtime API for nothing in particular (no category where it leads by five points or more).

## Score by category

| Category | Weight | Deepgram Voice Agent API | Ultravox Realtime API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 55 | 52 | Deepgram Voice Agent API +3 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 90 | 84 | Deepgram Voice Agent API +6 |
| Agent ergonomics | 13% (16.2 this run) | 67 | 69 | Ultravox Realtime API +2 |
| Security & auth | 14% (17.5 this run) | 71 | 46 | Deepgram Voice Agent API +25 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 85 | 43 | Deepgram Voice Agent API +42 |
| Transparency & trust | 7% (8.8 this run) | 80 | 75 | Deepgram Voice Agent API +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **68.4 · B** | **58.6 · C** | |

## Facts side by side

| Fact | Deepgram Voice Agent API | Ultravox Realtime API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Deepgram | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://agent.deepgram.com/v1/agent` | `https://api.ultravox.ai/api` |
| Transports | HTTP, Streamable HTTP, stdio, SSE (legacy) | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | 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 | 2026-09-30 | 2026-07-18 |
| Popularity | 468 stars, 1.1M npm/wk, 805k PyPI/wk | 4.6k stars, 17k npm/wk |
| Agent reviews | 3/5 (2) | 3/5 (2) |

## Verdicts

**Deepgram Voice Agent API.** $0.075 a minute all in on Standard, $0.050 with your own LLM and TTS, $200 of credit with no card. No phone numbers or SIP, so you bridge Twilio or another carrier yourself.

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

## Before you call either

### Deepgram Voice Agent API

1. Set `mip_opt_out` in the Settings message to keep call audio out of training
2. Use the function-call hold for anything irreversible, since replies can start before the user's turn is confirmed
3. Back off exponentially on 429, a pay-as-you-go project gets 45 concurrent sockets
4. Pin the LLM version, an unpinned Gemini route failed for 1.5 hours on 21 July 2026
5. Mint browser tokens with `ttl_seconds`, not `ttl`, or they expire after 30 seconds

### 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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