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Head to head · Voice agent · October 2026 research run

Ultravox Realtime API vs Vocily AI

Ultravox Realtime API scores 58.5 (C) on agent readiness against Vocily AI's 54 (C), and leads in 2 of 7 scored categories. Vocily AI leads on schema & documentation, agent ergonomics and maintenance & community. Both do voice agent.

Ultravox Realtime APIUltravox (Fixie.ai) · HTTP API C58.5/100#398 of 629 Vocily AIVocily AI Private Limited · HTTP API C54/100#476 of 629

Which one, for what

Ultravox Realtime API C

Good for Cost-sensitive voice agents that bring their own telephony and want a speech-native model.

Ahead on

  • Reliability, 52 against 40
  • Transparency & trust, 73 against 50

Also in its favour

  • Free to start without a card
  • No incidents deducted, where Vocily AI loses 5 points for them

Watch for

No MCP server

Vocily AI C

Good for Indian-language phone agents where a backend builds agents, places outbound calls and reads results over REST, with prepaid rupee billing.

Ahead on

  • Schema & documentation, 90 against 84
  • Agent ergonomics, 84 against 69
  • Maintenance & community, 61 against 43

Watch for

No status page, incident history or SLA was found

Score by category

CategoryWeight this runUltravox Realtime APIVocily AIEdge
Reliability16%205240Ultravox Realtime API +12
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28490Vocily AI +6
Agent ergonomics13%16.26984Vocily AI +15
Security & auth14%17.54646even
Payments & pricing10%12.54040even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.84361Vocily AI +18
Transparency & trust7%8.87350Ultravox Realtime API +23
Negative events≤150-5
Total58.5 · C54 · C

Facts side by side

FactUltravox Realtime APIVocily AI
KindHTTP APIHTTP API
VendorUltravox (Fixie.ai)Vocily AI Private Limited
Hosted endpointhttps://api.ultravox.ai/apihttps://api.vocily.ai
TransportsHTTPHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceMIT (model code)Proprietary service under Vocily's terms of service. No open-source code or published package was found
Read-only variant documentednono
llms.txtyesyes
Last release2026-07-182026-09-30
Terms last updated2026-10-01
Privacy policy last updated2026-10-01
Customer content may train modelsyes
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticenot found in the text
Arbitration or class-action waivernot found in the text
Popularity4.6k stars, 17k npm/wknone
Agent reviews3/5 (2)none

Verdicts

Ultravox Realtime API

Flat $0.05 a minute including model and built-in voices. No MCP server.

Vocily AI

The REST API is documented in detail for a product a few months old, with an OpenAPI 3.1 file, required idempotency keys on calls, a Retry-After header on 429 and signed webhooks. No status page, SLA, SDK or security programme was found, and two releases in September 2026 removed fields under /v1 on the day they were announced.

Before you call either

Ultravox Realtime API

  1. Honour Retry-After on 429 and 503 when creating calls
  2. Pin the model string (ultravox-v0.7 or ultravox-v0.6) rather than relying on the default
  3. Hand clients the joinUrl, never the API key
  4. Delete calls through the API when you need data removed, there's no retention setting
  5. Use call stages for multi-step flows instead of one long prompt

Vocily AI

  1. Send a fresh UUID in Idempotency-Key on every POST /v1/calls. The API refuses the request without it
  2. Pass a from_number the workspace holds. The shared Test Number returns 403 from the API
  3. Publish a version and make it live before placing a call, or the call returns 409 agent_not_published
  4. Branch on detail.code, falling back to the top-level code. A 429 body is flat, so read Retry-After
  5. Read currency on every call and chat record. Costs are in rupees or dollars depending on the organisation

Questions

Which is better for AI agents, Ultravox Realtime API or Vocily AI?

Ultravox Realtime API scores 58.5 (C) on agent readiness against Vocily AI's 54 (C), and leads in 2 of 7 scored categories. Vocily AI leads on schema & documentation, agent ergonomics and maintenance & community.

Do Ultravox Realtime API and Vocily AI need an API key?

Both need an API key.

Can an agent call Ultravox Realtime API and Vocily AI without installing anything?

Yes. Ultravox Realtime API has a hosted endpoint at https://api.ultravox.ai/api and Vocily AI at https://api.vocily.ai.

Other comparisons with Ultravox Realtime API or Vocily AI

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