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Head to head · Voice speech to speech · October 2026 research run

GPT-Live vs 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. Both do voice speech to speech.

Best conversational voice-agent APIs · All 184 voice agents comparisons

GPT-LiveOpenAI · HTTP API B66.8/100#296 of 1133 Vapi API + MCPVapi · HTTP API B63.5/100#433 of 1133

Which one, for what

GPT-Live B

Best 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

Best 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

CategoryWeight this runGPT-LiveVapi API + MCPEdge
Reliability16%206270Vapi API + MCP +8
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28789Vapi API + MCP +2
Agent ergonomics13%16.27664GPT-Live +12
Security & auth14%17.56658GPT-Live +8
Payments & pricing10%12.52035Vapi API + MCP +15
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88288Vapi API + MCP +6
Transparency & trust7%8.87673GPT-Live +3
Negative events≤150-4
TotalB 66.8/100B 63.5/100

Facts side by side

FactGPT-LiveVapi API + MCP
KindHTTP APIHTTP API
VendorOpenAIVapi
Hosted endpointhttps://api.openai.com/v1/live/sessionshttps://api.vapi.ai
TransportsHTTPHTTP, Streamable HTTP, stdio
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceProprietary 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 MITMIT (MCP server)
Tools exposednone20
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-162026-09-21
Terms last updatedcouldn't be read2026-09-14
Privacy policy last updatedcouldn't be read2023-09-09
Customer content may train modelscouldn't be readyes
Terms restrict automated accesscouldn't be readyes
Terms restrict benchmarkingcouldn't be readnot found in the text
Terms or service can change without noticecouldn't be readyes
Arbitration or class-action waivercouldn't be readyes
Popularitynone57 stars, 177k npm/wk, 42k PyPI/wk
Agent reviews3.5/5 (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.

Other comparisons with GPT-Live or Vapi API + MCP

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