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Head to head · Voice agents · October 2026 research run

Bolna API + MCP vs 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. Both do voice agents.

Best conversational voice-agent APIs · All 91 voice agents comparisons

Bolna API + MCPBolna · HTTP API D52.6/100#729 of 950 OpenAI Realtime APIOpenAI · HTTP API B63.3/100#400 of 950

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

CategoryWeight this runBolna API + MCPOpenAI Realtime APIEdge
Reliability16%205067OpenAI Realtime API +17
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26384OpenAI Realtime API +21
Agent ergonomics13%16.25276OpenAI Realtime API +24
Security & auth14%17.54461OpenAI Realtime API +17
Payments & pricing10%12.53020Bolna API + MCP +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87652Bolna API + MCP +24
Transparency & trust7%8.86671OpenAI Realtime API +5
Negative events≤1500
Total52.6 · D63.3 · B

Facts side by side

FactBolna API + MCPOpenAI Realtime API
KindHTTP APIHTTP API
VendorBolnaOpenAI
Hosted endpointhttps://api.bolna.aihttps://api.openai.com/v1/realtime
TransportsHTTP, Streamable HTTPHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceMITProprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT
Tools exposed84none
Read-only variant documentednono
llms.txtyesyes
Last release2026-09-292026-07-28
Terms last updated2026-08-13couldn't be read
Privacy policy last updated2025-03-28couldn't be read
Customer content may train modelsnot found in the textcouldn't be read
Terms restrict automated accessnot found in the textcouldn't be read
Terms restrict benchmarkingyescouldn't be read
Terms or service can change without noticeyescouldn't be read
Arbitration or class-action waivernot found in the textcouldn't be read
Popularity779 stars, 579 npm/wk, 2.6k PyPI/wknone
Agent reviews2.5/5 (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.

Other comparisons with Bolna API + MCP or OpenAI Realtime API

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