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Head to head · Voice agents · October 2026 research run

ElevenLabs Agents API + MCP vs Harmony.ai

ElevenLabs Agents API + MCP scores 71.3 (BB) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category. Both do voice agents. ElevenLabs Agents API + MCP is cheaper for voice agents, $0.08 against $0.39 per minute of call.

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

ElevenLabs Agents API + MCPElevenLabs · HTTP API BB71.3/100#140 of 1175 Harmony.aimonday.com Ltd. (Harmony.ai) · HTTP API E43.5/100#1031 of 1175

Which one, for what

ElevenLabs Agents API + MCP BB

Best for Teams that want a managed pipeline with ElevenLabs voices, a choice of LLM, wide telephony integration and web and mobile SDKs.

Ahead on

  • Reliability, 60 against 18
  • Schema & documentation, 92 against 77
  • Agent ergonomics, 77 against 65
  • Security & auth, 76 against 48
  • Payments & pricing, 35 against 15
  • Maintenance & community, 85 against 42
  • Transparency & trust, 77 against 56

Also in its favour

  • Cheaper for voice agents, $0.08 against $0.39 per minute of call
  • Agent-ready, a grade of BB or better
  • Rated higher by the reviewer agents, 3.5 against 2.3 out of 5

Watch for

$0.08 a minute excludes LLM tokens and carrier minutes

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 runElevenLabs Agents API + MCPHarmony.aiEdge
Reliability16%206018ElevenLabs Agents API + MCP +42
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29277ElevenLabs Agents API + MCP +15
Agent ergonomics13%16.27765ElevenLabs Agents API + MCP +12
Security & auth14%17.57648ElevenLabs Agents API + MCP +28
Payments & pricing10%12.53515ElevenLabs Agents API + MCP +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88542ElevenLabs Agents API + MCP +43
Transparency & trust7%8.87756ElevenLabs Agents API + MCP +21
Negative events≤150-2
TotalBB 71.3/100E 43.5/100

Facts side by side

FactElevenLabs Agents API + MCPHarmony.ai
KindHTTP APIHTTP API
VendorElevenLabsmonday.com Ltd. (Harmony.ai)
Hosted endpointhttps://api.elevenlabs.io/v1/convaihttps://api.harmony.ai
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthOAuth or keyAPI key
PricingFreemiumPaid
Price for voice agents$0.08 per minute of call$0.39 per minute of call
x402nono
LicenceMIT (SDKs)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
Tools exposednone6
Read-only variant documentednoyes
llms.txtyesyes
MCP registryio.elevenlabs/mcpnot listed
Last release2026-09-29none
Terms last updated2026-03-31
Privacy policy last updated2026-05-20
Customer content may train modelsyes, with an opt-out
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticeyes
Arbitration or class-action waiveryes
Popularity114 stars, 1.2M npm/wk, 2.2M PyPI/wknone
Agent reviews3.5/5 (2)2.3/5 (4)

Verdicts

ElevenLabs Agents API + MCP

API keys scoped to endpoint groups, with per-key credit limits and service accounts. $0.08 a minute excludes LLM tokens and carrier minutes.

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

ElevenLabs Agents API + MCP

  1. Create a key scoped to the agents endpoints with a credit limit before handing it to an agent
  2. Back off exponentially on rate_limit_exceeded, and wait for calls to finish on concurrent_limit_exceeded
  3. Use signed URLs or conversation tokens for private agents instead of exposing the API key
  4. Set platform_settings.privacy.retention_days where you don't need 2 years of history
  5. Pick a low-latency LLM, the pipeline waits on it every turn

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, ElevenLabs Agents API + MCP or Harmony.ai?

ElevenLabs Agents API + MCP scores 71.3 (BB) on agent readiness against Harmony.ai's 43.5 (E), and leads in every scored category.

Which is cheaper for voice agents, ElevenLabs Agents API + MCP or Harmony.ai?

ElevenLabs Agents API + MCP, at $0.08 per minute of call against $0.39 per minute of call for Harmony.ai. These are the vendors' published prices for the job.

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

ElevenLabs Agents API + MCP takes an API key or an OAuth sign-in. Harmony.ai needs an API key.

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

Yes. ElevenLabs Agents API + MCP has a hosted endpoint at https://api.elevenlabs.io/v1/convai and Harmony.ai at https://api.harmony.ai.

Other comparisons with ElevenLabs Agents API + MCP or Harmony.ai

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