Ultravox Realtime API vs Vogent API

Ultravox Realtime API

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

Vogent API

IVR detection and navigation models for outbound calls. No public changelog and no release found since January 2026.

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

Vogent API

1. Send an idempotencyKey on POST /dials, a reused key returns 409
2. Create a call with callAgentId, plus toNumber and fromNumberId for phone calls
3. Tell the model when to emit <|transfer|>, since transfers fire on that tag
4. Verify webhooks with the HMAC in X-Elto-Signature
5. Expect new dials to fail at the workspace's concurrent dial limit until calls end