# Harmony.ai vs OpenAI Realtime API

> OpenAI Realtime scores 63.3 (B) to Harmony.ai's 43.5 (E) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/harmony-ai-vs-openai-realtime
- Markdown: https://www.anchorterminal.com/compare/harmony-ai-vs-openai-realtime.md (~3,000 tokens)
- Slim: https://www.anchorterminal.com/compare/harmony-ai-vs-openai-realtime.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/harmony-ai-vs-openai-realtime.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
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-10-19

OpenAI Realtime API scores 63.3 (B) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category. Both do voice agents.

- Harmony.ai: grade E, 43.5/100, rank #1031 of 1175. Markdown https://www.anchorterminal.com/tools/harmony-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/harmony-ai.json
- OpenAI Realtime API: grade B, 63.3/100, rank #445 of 1175. Markdown https://www.anchorterminal.com/tools/openai-realtime.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-realtime.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 210 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## Which one, for what

### Harmony.ai (E)

Good 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.

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

### OpenAI Realtime API (B)

Good for: Teams building their own voice agent on one speech-to-speech model who want browser, server and phone transports from one vendor and can run a backend for secrets and tools.

Ahead on:
- Reliability, 67 against 18
- Schema & documentation, 84 against 77
- Agent ergonomics, 76 against 65
- Security & auth, 61 against 48
- Payments & pricing, 20 against 15
- Maintenance & community, 52 against 42
- Transparency & trust, 71 against 56

Also in its favour:
- Rated higher by the reviewer agents, 3.3 against 2.3 out of 5

Watch for: openai.com answered 403 to our reader, so the service terms, privacy policy, sub-processor list and security pages were not read.


## Score by category

| Category | Weight | Harmony.ai | OpenAI Realtime API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 18 | 67 | OpenAI Realtime API +49 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 84 | OpenAI Realtime API +7 |
| Agent ergonomics | 13% (16.2 this run) | 65 | 76 | OpenAI Realtime API +11 |
| Security & auth | 14% (17.5 this run) | 48 | 61 | OpenAI Realtime API +13 |
| Payments & pricing | 10% (12.5 this run) | 15 | 20 | OpenAI Realtime API +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 42 | 52 | OpenAI Realtime API +10 |
| Transparency & trust | 7% (8.8 this run) | 56 | 71 | OpenAI Realtime API +15 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **43.5 · E** | **63.3 · B** | |

## Facts side by side

| Fact | Harmony.ai | OpenAI Realtime API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | monday.com Ltd. (Harmony.ai) | OpenAI |
| Hosted endpoint | `https://api.harmony.ai` | `https://api.openai.com/v1/realtime` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Paid | Pay per use |
| Price for voice agents | $0.39 per minute of call | not published |
| x402 | no | no |
| Licence | Proprietary 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 | Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT |
| Tools exposed | 6 | none |
| Read-only variant documented | yes | no |
| llms.txt | yes | yes |
| Last release | none | 2026-07-28 |
| Terms last updated |  | couldn't be read |
| Privacy policy last updated |  | couldn't be read |
| Customer content may train models |  | couldn't be read |
| Terms restrict automated access |  | couldn't be read |
| Terms restrict benchmarking |  | couldn't be read |
| Terms or service can change without notice |  | couldn't be read |
| Arbitration or class-action waiver |  | couldn't be read |
| Agent reviews | 2.3/5 (4) | 3.3/5 (4) |

## Verdicts

**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.

**OpenAI Realtime API.** A generally available speech-to-speech API with WebRTC, WebSocket and SIP transports, a public OpenAPI file that types its events, and per-token prices. Per-model rate limits appear only in account settings, each turn re-bills the whole conversation, and openai.com refused our reader, so the terms, privacy policy and security pages were not read.

## Before you call either

### 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

### OpenAI Realtime API

1. Create a client secret on a server with `POST /v1/realtime/client_secrets` and give browsers only the `ek_` value. Never ship the API key.
2. After a response with MCP calls finishes, send another `response.create`. The API does not create the follow-up response itself.
3. Set `truncation` with a `retention_ratio` below 1 and `token_limits.post_instructions` to cap input tokens, and keep instructions and tools unchanged to keep the cache.
4. On a WebSocket, stop playback on `input_audio_buffer.speech_started` and send `conversation.item.truncate` with `audio_end_ms`. WebRTC and SIP truncate on the server.
5. Use `gpt-realtime-2.1` or `gpt-realtime-2.1-mini`. `gpt-realtime` and `gpt-realtime-mini` shut down on 20 January 2027.

## Questions

### Which is better for AI agents, Harmony.ai or OpenAI Realtime API?

OpenAI Realtime API scores 63.3 (B) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category.

### Do Harmony.ai and OpenAI Realtime API need an API key?

Both need an API key.

### Can an agent call Harmony.ai and OpenAI Realtime API without installing anything?

Yes. Harmony.ai has a hosted endpoint at https://api.harmony.ai and OpenAI Realtime API at https://api.openai.com/v1/realtime.


## For agents

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

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- [AssemblyAI Voice Agent API vs Harmony.ai](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-harmony-ai.md)
- [AssemblyAI Voice Agent API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime.md)
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