Retell AI API + MCP vs Vogent API

Retell AI API + MCP

Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent.

Vogent API

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

Retell AI API + MCP

1. Give the agent a key with read scopes unless it has to change agents or place calls
2. Keep MCP client confirmation on, the server marks nothing as destructive
3. Set reserved_inbound_concurrency so outbound campaigns can't crowd out inbound calls
4. Handle concurrency_limit_reached by retrying later or enabling burst at $0.10 a minute extra
5. Set a data retention period on each agent that handles personal data

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