Call

Ready when you are

Uses your microphone. Calls last up to three minutes.

App key Language

Developer options

Language is sent with the session as a BCP-47 tag, so transcription, the assistant and the voice all use it. "Match what I speak" clears any language the agent is pinned to and mirrors the caller instead.

User ID optional Thread ID User context (JSON) Metadata (JSON)

Both are sent with the session and reach the assistant's system prompt as conversation context.