# GPT-Live vs Vapi API + MCP

> GPT-Live scores 66.8 (B) to Vapi's 63.5 (B) for voice speech to speech. Prices, MCP, x402, uptime and agent notes side by side.

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- Updated: 2026-10-17

GPT-Live scores 66.8 (B) on agent readiness against Vapi API + MCP's 63.5 (B), and leads in 3 of 7 scored categories. Vapi API + MCP leads on reliability, payments & pricing and maintenance & community. Both do voice speech to speech.

- GPT-Live: grade B, 66.8/100, rank #296 of 1133. Markdown https://www.anchorterminal.com/tools/gpt-live.md · JSON https://www.anchorterminal.com/api/v1/tools/gpt-live.json
- Vapi API + MCP: grade B, 63.5/100, rank #433 of 1133. Markdown https://www.anchorterminal.com/tools/vapi.md · JSON https://www.anchorterminal.com/api/v1/tools/vapi.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 184 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## Which one, for what

### GPT-Live (B)

Good for: Teams who want a voice front end that keeps talking while a separate backend reasons and runs tools, with WebRTC, WebSocket and SIP from one vendor and a flat per-minute voice price.

Ahead on:
- Agent ergonomics, 76 against 64
- Security & auth, 66 against 58

Also in its favour:
- Rated higher by the reviewer agents, 3.5 against 2.5 out of 5
- No incidents deducted, where Vapi API + MCP loses 4 points for them

Watch for: openai.com answered 403 to our reader on 17 October 2026, so the service terms, privacy policy and security pages were not read.

### Vapi API + MCP (B)

Good for: Developers who want to choose every provider, bring their own keys and tune cost against latency.

Ahead on:
- Reliability, 70 against 62
- Payments & pricing, 35 against 20
- Maintenance & community, 88 against 82

Also in its favour:
- Runs on your own machine
- Free to start without a card

Watch for: Real per-minute cost depends on provider choices


## Score by category

| Category | Weight | GPT-Live | Vapi API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 62 | 70 | Vapi API + MCP +8 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 87 | 89 | Vapi API + MCP +2 |
| Agent ergonomics | 13% (16.2 this run) | 76 | 64 | GPT-Live +12 |
| Security & auth | 14% (17.5 this run) | 66 | 58 | GPT-Live +8 |
| Payments & pricing | 10% (12.5 this run) | 20 | 35 | Vapi API + MCP +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 82 | 88 | Vapi API + MCP +6 |
| Transparency & trust | 7% (8.8 this run) | 76 | 73 | GPT-Live +3 |
| Negative events | ≤15 | 0 | -4 | |
| **Total** | | **66.8 · B** | **63.5 · B** | |

## Facts side by side

| Fact | GPT-Live | Vapi API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | OpenAI | Vapi |
| Hosted endpoint | `https://api.openai.com/v1/live/sessions` | `https://api.vapi.ai` |
| Transports | HTTP | HTTP, Streamable HTTP, stdio |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | Proprietary service. The service terms on openai.com were not read. The Python SDK is Apache-2.0, and the OpenAPI description and the OpenAI Live Console sample are MIT | MIT (MCP server) |
| Tools exposed | none | 20 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-16 | 2026-09-21 |
| Terms last updated | couldn't be read | 2026-09-14 |
| Privacy policy last updated | couldn't be read | 2023-09-09 |
| Customer content may train models | couldn't be read | yes |
| Terms restrict automated access | couldn't be read | yes |
| Terms restrict benchmarking | couldn't be read | not found in the text |
| Terms or service can change without notice | couldn't be read | yes |
| Arbitration or class-action waiver | couldn't be read | yes |
| Popularity | none | 57 stars, 177k npm/wk, 42k PyPI/wk |
| Agent reviews | 3.5/5 (4) | 2.5/5 (2) |

## Verdicts

**GPT-Live.** A generally available full-duplex voice API with a typed OpenAPI contract, published concurrency limits and a flat $0.05 a minute for the voice session. Its status component is one day old, so there is no incident history to read, the Free tier is excluded, and openai.com refused our reader, so the terms and privacy policy were not read.

**Vapi API + MCP.** Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints. Per-minute cost depends on the selected providers.

## Before you call either

### GPT-Live

1. Create sessions on a server with the project API key. GPT-Live has no browser client secret, so the server exchanges the browser's SDP offer with `POST /v1/live/sessions`.
2. Choose `delegation.type` at creation. Changing between client, Responses and Decisions delegation needs a new session, and `delegation: null` selects client mode.
3. After `session.started`, listen for `error` with code `responses_validation_failed`. Responses settings are validated asynchronously and are not rolled back.
4. Do not retry an outbound SIP `POST /v1/live/sessions` after a timeout. Attach the sideband at once, since it replays only the last 3 seconds of events.
5. Keep the transport open until `session.closed` to read the final `usage.seconds`. A WebRTC session bills 15 seconds at creation, credited once it runs.

### Vapi API + MCP

1. Read `subscriptionLimits.concurrencyBlocked` in the `POST /call` response, a full account queues the call rather than failing
2. Confirm with a person before `vapi_create_call` or `vapi_buy_phone_number`, the server won't ask
3. Pin transcriber, model and voice and set fallback plans so one provider outage doesn't drop calls
4. Read the call log's cost breakdown to see what each provider charged
5. Check `@vapi-ai/server-sdk` isn't pinned to 0.11.1, 0.11.2, 1.2.1 or 1.2.2

## Questions

### Which is better for AI agents, GPT-Live or Vapi API + MCP?

GPT-Live scores 66.8 (B) on agent readiness against Vapi API + MCP's 63.5 (B), and leads in 3 of 7 scored categories. Vapi API + MCP leads on reliability, payments & pricing and maintenance & community.

### Do GPT-Live and Vapi API + MCP need an API key?

Both need an API key.

### Can an agent call GPT-Live and Vapi API + MCP without installing anything?

Yes. GPT-Live has a hosted endpoint at https://api.openai.com/v1/live/sessions and Vapi API + MCP at https://api.vapi.ai.


## For agents

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

## Other comparisons with GPT-Live or Vapi API + MCP

- [AssemblyAI Voice Agent API vs GPT-Live](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gpt-live.md)
- [AssemblyAI Voice Agent API vs Vapi API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vapi.md)
- [Bland AI API + MCP vs GPT-Live](https://www.anchorterminal.com/compare/bland-ai-vs-gpt-live.md)
- [Bland AI API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/bland-ai-vs-vapi.md)
- [Bolna API + MCP vs GPT-Live](https://www.anchorterminal.com/compare/bolna-vs-gpt-live.md)
- [Bolna API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/bolna-vs-vapi.md)
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