# Harmony.ai vs Ultravox Realtime API (slim)

> Ultravox Realtime scores 58.5 (C) to Harmony.ai's 43.5 (E) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox.md (~2,700 tokens) · this version ~730 tokens · JSON https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox.json · canonical https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-10-19
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)

Ultravox Realtime API scores 58.5 (C) on agent readiness against Harmony.ai's 43.5 (E), and leads in 6 of 7 scored categories. Both do voice agents.

- Harmony.ai: E 43.5, rank #1031 of 1175 · https://www.anchorterminal.com/tools/harmony-ai.min.md
- Ultravox Realtime API: C 58.5, rank #643 of 1175 · https://www.anchorterminal.com/tools/ultravox.min.md
- Harmony.ai, good 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.
- Ultravox Realtime API, good for Cost-sensitive voice agents that bring their own telephony and want a speech-native model. Ahead on Reliability, 52 against 18; Schema & documentation, 84 against 77; Payments & pricing, 40 against 15; Transparency & trust, 73 against 56. Also Free to start without a card; Rated higher by the reviewer agents, 3.0 against 2.3 out of 5.

| Category | Harmony.ai | Ultravox Realtime API |
| --- | --- | --- |
| Reliability (16%) | 18 | 52 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 77 | 84 |
| Agent ergonomics (13%) | 65 | 69 |
| Security & auth (14%) | 48 | 46 |
| Payments & pricing (10%) | 15 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 42 | 43 |
| Transparency & trust (7%) | 56 | 73 |

| Fact (where they differ) | Harmony.ai | Ultravox Realtime API |
| --- | --- | --- |
| Vendor | monday.com Ltd. (Harmony.ai) | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://api.harmony.ai` | `https://api.ultravox.ai/api` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Pricing | Paid | Pay per use |
| Price for voice agents | $0.39 per minute of call | not published |
| Licence | 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 | MIT (model code) |
| Tools exposed | 6 | none |
| Read-only variant documented | yes | no |
| Last release | none | 2026-07-18 |
| Terms last updated |  | 2026-10-01 |
| Privacy policy last updated |  | 2026-10-01 |
| Customer content may train models |  | yes |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | none | 4.6k stars, 17k npm/wk |
| Agent reviews | 2.3/5 (4) | 3/5 (2) |