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Head to head · Voice agents · October 2026 research run

Bolna API + MCP vs Harmony.ai

Bolna API + MCP scores 52.6 (D) on agent readiness against Harmony.ai's 43.5 (E), and leads in 4 of 7 scored categories. Harmony.ai leads on schema & documentation and agent ergonomics. Both do voice agents.

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

Bolna API + MCPBolna · HTTP API D52.6/100#831 of 1175 Harmony.aimonday.com Ltd. (Harmony.ai) · HTTP API E43.5/100#1031 of 1175

Which one, for what

Bolna API + MCP D

Best 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

  • Reliability, 50 against 18
  • Payments & pricing, 30 against 15
  • Maintenance & community, 76 against 42
  • Transparency & trust, 66 against 56

Also in its favour

  • Open source

Watch for

Unsigned webhooks and tool calls, IP allowlisting only

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.

Ahead on

  • Schema & documentation, 77 against 63
  • Agent ergonomics, 65 against 52

Watch for

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

Score by category

CategoryWeight this runBolna API + MCPHarmony.aiEdge
Reliability16%205018Bolna API + MCP +32
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26377Harmony.ai +14
Agent ergonomics13%16.25265Harmony.ai +13
Security & auth14%17.54448Harmony.ai +4
Payments & pricing10%12.53015Bolna API + MCP +15
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87642Bolna API + MCP +34
Transparency & trust7%8.86656Bolna API + MCP +10
Negative events≤150-2
TotalD 52.6/100E 43.5/100

Facts side by side

FactBolna API + MCPHarmony.ai
KindHTTP APIHTTP API
VendorBolnamonday.com Ltd. (Harmony.ai)
Hosted endpointhttps://api.bolna.aihttps://api.harmony.ai
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthAPI keyAPI key
PricingPay per usePaid
Price for voice agentsnot published$0.39 per minute of call
x402nono
LicenceMITProprietary 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 exposed846
Read-only variant documentednoyes
llms.txtyesyes
Last release2026-09-29none
Terms last updated2026-08-13
Privacy policy last updated2025-03-28
Customer content may train modelsnot found in the text
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingyes
Terms or service can change without noticeyes
Arbitration or class-action waivernot found in the text
Popularity779 stars, 579 npm/wk, 2.6k PyPI/wknone
Agent reviews2.5/5 (2)2.3/5 (4)

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.

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

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

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, Bolna API + MCP or Harmony.ai?

Bolna API + MCP scores 52.6 (D) on agent readiness against Harmony.ai's 43.5 (E), and leads in 4 of 7 scored categories. Harmony.ai leads on schema & documentation and agent ergonomics.

Do Bolna API + MCP and Harmony.ai need an API key?

Both need an API key.

Can an agent call Bolna API + MCP and Harmony.ai without installing anything?

Yes. Bolna API + MCP has a hosted endpoint at https://api.bolna.ai and Harmony.ai at https://api.harmony.ai.

Are Bolna API + MCP and Harmony.ai open source?

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

Other comparisons with Bolna API + MCP or Harmony.ai

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