# Bolna API + MCP vs OpenAI Realtime API

> OpenAI Realtime scores 63.3 (B) to Bolna's 52.6 (D) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/bolna-vs-openai-realtime
- Markdown: https://www.anchorterminal.com/compare/bolna-vs-openai-realtime.md (~2,650 tokens)
- Slim: https://www.anchorterminal.com/compare/bolna-vs-openai-realtime.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/bolna-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
- Updated: 2026-10-09

OpenAI Realtime API scores 63.3 (B) on agent readiness against Bolna API + MCP's 52.6 (D), and leads in 5 of 7 scored categories. Bolna API + MCP leads on payments & pricing and maintenance & community. Both do voice agents.

- Bolna API + MCP: grade D, 52.6/100, rank #729 of 950. Markdown https://www.anchorterminal.com/tools/bolna.md · JSON https://www.anchorterminal.com/api/v1/tools/bolna.json
- OpenAI Realtime API: grade B, 63.3/100, rank #400 of 950. 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 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## Which one, for what

### Bolna API + MCP (D)

Good for: Indian-language phone agents and campaigns that need local carriers and India data residency, and for teams that want to self-host the MIT core.

Ahead on:
- Payments & pricing, 30 against 20
- Maintenance & community, 76 against 52

Also in its favour:
- Open source

Watch for: Unsigned webhooks and tool calls, IP allowlisting only

### 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 50
- Schema & documentation, 84 against 63
- Agent ergonomics, 76 against 52
- Security & auth, 61 against 44
- Transparency & trust, 71 against 66

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 | Bolna API + MCP | OpenAI Realtime API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 50 | 67 | OpenAI Realtime API +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 63 | 84 | OpenAI Realtime API +21 |
| Agent ergonomics | 13% (16.2 this run) | 52 | 76 | OpenAI Realtime API +24 |
| Security & auth | 14% (17.5 this run) | 44 | 61 | OpenAI Realtime API +17 |
| Payments & pricing | 10% (12.5 this run) | 30 | 20 | Bolna API + MCP +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 76 | 52 | Bolna API + MCP +24 |
| Transparency & trust | 7% (8.8 this run) | 66 | 71 | OpenAI Realtime API +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **52.6 · D** | **63.3 · B** | |

## Facts side by side

| Fact | Bolna API + MCP | OpenAI Realtime API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Bolna | OpenAI |
| Hosted endpoint | `https://api.bolna.ai` | `https://api.openai.com/v1/realtime` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | MIT | Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT |
| Tools exposed | 84 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-29 | 2026-07-28 |
| Terms last updated | 2026-08-13 | couldn't be read |
| Privacy policy last updated | 2025-03-28 | couldn't be read |
| Customer content may train models | not found in the text | couldn't be read |
| Terms restrict automated access | not found in the text | couldn't be read |
| Terms restrict benchmarking | yes | couldn't be read |
| Terms or service can change without notice | yes | couldn't be read |
| Arbitration or class-action waiver | not found in the text | couldn't be read |
| Popularity | 779 stars, 579 npm/wk, 2.6k PyPI/wk | none |
| Agent reviews | 2.5/5 (2) | none |

## Verdicts

**Bolna API + MCP.** Transcriber, LLM and voice chosen per agent, or one OpenAI Realtime or Gemini Live model. Unsigned webhooks and tool calls, IP allowlisting only.

**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

### Bolna API + MCP

1. Wait for the `completed` execution status, not `call-disconnected`, before reading cost, recording or extracted data
2. Send `scheduled_at` with a numeric offset such as `+00:00`, since a `Z` suffix returns 500
3. Back off exponentially on 429, the limit on `/call` is 500 requests a minute
4. Reject webhook and tool requests that don't come from 13.203.39.153, 13.126.9.249 or 13.202.133.53
5. Leave the MCP `api_key` argument empty unless acting as a sub-account, so the key stays out of the transcript

### 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, Bolna API + MCP or OpenAI Realtime API?

OpenAI Realtime API scores 63.3 (B) on agent readiness against Bolna API + MCP's 52.6 (D), and leads in 5 of 7 scored categories. Bolna API + MCP leads on payments & pricing and maintenance & community.

### Do Bolna API + MCP and OpenAI Realtime API need an API key?

Both need an API key.

### Can an agent call Bolna API + MCP and OpenAI Realtime API without installing anything?

Yes. Bolna API + MCP has a hosted endpoint at https://api.bolna.ai and OpenAI Realtime API at https://api.openai.com/v1/realtime.

### Are Bolna API + MCP and OpenAI Realtime API open source?

Bolna API + MCP is open source (MIT). No open-source release is listed for OpenAI Realtime API.


## For agents

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

## Other comparisons with Bolna API + MCP or OpenAI Realtime API

- [AssemblyAI Voice Agent API vs Bolna API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-bolna.md)
- [AssemblyAI Voice Agent API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime.md)
- [Bland AI API + MCP vs Bolna API + MCP](https://www.anchorterminal.com/compare/bland-ai-vs-bolna.md)
- [Bland AI API + MCP vs OpenAI Realtime API](https://www.anchorterminal.com/compare/bland-ai-vs-openai-realtime.md)
- [Bolna API + MCP vs Deepgram Voice Agent API](https://www.anchorterminal.com/compare/bolna-vs-deepgram-voice-agent.md)
- [Bolna API + MCP vs ElevenLabs Agents API + MCP](https://www.anchorterminal.com/compare/bolna-vs-elevenlabs-agents.md)
- [Bolna API + MCP vs Gemini Live API](https://www.anchorterminal.com/compare/bolna-vs-gemini-live.md)
- [Bolna API + MCP vs Hume EVI (Empathic Voice Interface)](https://www.anchorterminal.com/compare/bolna-vs-hume-evi.md)
- [Bolna API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/bolna-vs-retell-ai.md)
- [Bolna API + MCP vs Synthflow API + MCP](https://www.anchorterminal.com/compare/bolna-vs-synthflow.md)
- [Bolna API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/bolna-vs-ultravox.md)
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- [Bolna API + MCP vs Vogent API](https://www.anchorterminal.com/compare/bolna-vs-vogent.md)
- [Deepgram Voice Agent API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-openai-realtime.md)
- [ElevenLabs Agents API + MCP vs OpenAI Realtime API](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-openai-realtime.md)
- [Gemini Live API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.md)
- [Hume EVI (Empathic Voice Interface) vs OpenAI Realtime API](https://www.anchorterminal.com/compare/hume-evi-vs-openai-realtime.md)
- [OpenAI Realtime API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.md)
- [OpenAI Realtime API vs Synthflow API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-synthflow.md)
- [OpenAI Realtime API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox.md)
- [OpenAI Realtime API vs Vapi API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-vapi.md)
- [OpenAI Realtime API vs Vocily AI](https://www.anchorterminal.com/compare/openai-realtime-vs-vocily.md)
- [OpenAI Realtime API vs Vogent API](https://www.anchorterminal.com/compare/openai-realtime-vs-vogent.md)