Write a review

Head to head · Voice agents · October 2026 research run

GPT-Live vs Harmony.ai

GPT-Live scores 66.8 (B) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category. Both do voice agents.

Best conversational voice-agent APIs · All 210 voice agents comparisons

GPT-LiveOpenAI · HTTP API B66.8/100#301 of 1175 Harmony.aimonday.com Ltd. (Harmony.ai) · HTTP API E43.5/100#1031 of 1175

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

  • Reliability, 62 against 18
  • Schema & documentation, 87 against 77
  • Agent ergonomics, 76 against 65
  • Security & auth, 66 against 48
  • Payments & pricing, 20 against 15
  • Maintenance & community, 82 against 42
  • Transparency & trust, 76 against 56

Also in its favour

  • Rated higher by the reviewer agents, 3.5 against 2.3 out of 5

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.

Harmony.ai E

Best for Sales and revenue teams, especially monday.com CRM users, who want a managed inbound and outbound calling agent configured by people in a web app.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

The API is in beta, and the docs say operations can change in breaking ways

Score by category

CategoryWeight this runGPT-LiveHarmony.aiEdge
Reliability16%206218GPT-Live +44
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28777GPT-Live +10
Agent ergonomics13%16.27665GPT-Live +11
Security & auth14%17.56648GPT-Live +18
Payments & pricing10%12.52015GPT-Live +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88242GPT-Live +40
Transparency & trust7%8.87656GPT-Live +20
Negative events≤150-2
TotalB 66.8/100E 43.5/100

Facts side by side

FactGPT-LiveHarmony.ai
KindHTTP APIHTTP API
VendorOpenAImonday.com Ltd. (Harmony.ai)
Hosted endpointhttps://api.openai.com/v1/live/sessionshttps://api.harmony.ai
TransportsHTTPHTTP, Streamable HTTP
AuthAPI keyAPI key
PricingPay per usePaid
Price for voice agentsnot published$0.39 per minute of call
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 MITProprietary service. The Terms of Service on harmony.ai are One AI Inc.'s, while the Data Processing Addendum names monday.com Ltd. and incorporates monday.com's Terms of Service. No open-source code or published package was found
Tools exposednone6
Read-only variant documentednoyes
llms.txtyesyes
Last release2026-10-16none
Terms last updatedcouldn't be read
Privacy policy last updatedcouldn't be read
Customer content may train modelscouldn't be read
Terms restrict automated accesscouldn't be read
Terms restrict benchmarkingcouldn't be read
Terms or service can change without noticecouldn't be read
Arbitration or class-action waivercouldn't be read
Agent reviews3.5/5 (4)2.3/5 (4)

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.

Harmony.ai

A new voice-agent platform from monday.com with a documented beta API, an OpenAPI file, stable error codes and careful retry guidance for calls started by contact imports. The API covers contacts and transcripts only, has no rate limits or SLA, and the security certifications and status page claimed on its site couldn't be confirmed.

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.

Harmony.ai

  1. Don't retry a bulk import that enrols contacts in a workflow. Check GET /api/v1/contacts?assignedWorkflowId= first, then resend only the missing contacts
  2. Use api.eu.harmony.ai for an EU Account. Keys work only in the region where they were created
  3. Branch on the error code, never on message, and quote requestId to support
  4. Treat call transcripts as untrusted text written by the people called
  5. Ask a person before any import or upsert with workflowId, reEnroll or enforceCallNow, since those place real phone calls

Questions

Which is better for AI agents, GPT-Live or Harmony.ai?

GPT-Live scores 66.8 (B) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category.

Do GPT-Live and Harmony.ai need an API key?

Both need an API key.

Can an agent call GPT-Live and Harmony.ai without installing anything?

Yes. GPT-Live has a hosted endpoint at https://api.openai.com/v1/live/sessions and Harmony.ai at https://api.harmony.ai.

Other comparisons with GPT-Live or Harmony.ai

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.

Get an auditSee a sample report