# AssemblyAI Voice Agent API vs Deepgram Voice Agent API

> Deepgram Voice Agent scores 68.1 (B) 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-deepgram-voice-agent
- Markdown: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-deepgram-voice-agent.md (~2,750 tokens)
- Slim: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-deepgram-voice-agent.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-deepgram-voice-agent.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

Deepgram Voice Agent API scores 68.1 (B) on agent readiness against AssemblyAI Voice Agent API's 64.4 (B), and leads in 4 of 7 scored categories. AssemblyAI Voice Agent API leads on reliability and agent ergonomics. 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
- Deepgram Voice Agent API: grade B, 68.1/100, rank #228 of 950. Markdown https://www.anchorterminal.com/tools/deepgram-voice-agent.md · JSON https://www.anchorterminal.com/api/v1/tools/deepgram-voice-agent.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 67

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

### Deepgram Voice Agent API (B)

Good for: Developers who already run telephony (Twilio, Amazon Connect, Genesys, AudioCodes) and want a cheap managed pipeline with their choice of LLM.

Ahead on:
- Schema & documentation, 90 against 83
- Security & auth, 71 against 62
- Maintenance & community, 85 against 64
- Transparency & trust, 77 against 66

Also in its favour:
- Runs on your own machine

Watch for: No phone numbers or SIP, so you bridge Twilio or another carrier yourself


## Score by category

| Category | Weight | AssemblyAI Voice Agent API | Deepgram Voice Agent API | 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 | Deepgram Voice Agent API +7 |
| Agent ergonomics | 13% (16.2 this run) | 72 | 67 | AssemblyAI Voice Agent API +5 |
| Security & auth | 14% (17.5 this run) | 62 | 71 | Deepgram Voice Agent API +9 |
| 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) | 64 | 85 | Deepgram Voice Agent API +21 |
| Transparency & trust | 7% (8.8 this run) | 66 | 77 | Deepgram Voice Agent API +11 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **64.4 · B** | **68.1 · B** | |

## Facts side by side

| Fact | AssemblyAI Voice Agent API | Deepgram Voice Agent API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | AssemblyAI, Inc. | Deepgram |
| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `https://agent.deepgram.com/v1/agent` |
| Transports | HTTP | HTTP, Streamable HTTP, stdio, SSE (legacy) |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| 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 | 2026-09-30 |
| Terms last updated | 2026-07-01 | 2026-08-06 |
| Privacy policy last updated | 2026-05-26 | 2021-10-26 |
| 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 | 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 | 468 stars, 1.1M npm/wk, 805k PyPI/wk |
| Agent reviews | none | 3/5 (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.

**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.

## 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

### 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

## Questions

### Which is better for AI agents, AssemblyAI Voice Agent API or Deepgram Voice Agent API?

Deepgram Voice Agent API scores 68.1 (B) on agent readiness against AssemblyAI Voice Agent API's 64.4 (B), and leads in 4 of 7 scored categories. AssemblyAI Voice Agent API leads on reliability and agent ergonomics.

### Do AssemblyAI Voice Agent API and Deepgram Voice Agent API need an API key?

Both need an API key.

### Can an agent call AssemblyAI Voice Agent API and Deepgram Voice Agent API without installing anything?

Yes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and Deepgram Voice Agent API at https://agent.deepgram.com/v1/agent.


## For agents

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

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