curl --request POST \
  --url https://api.oneinbox.ai/v1/calls/web \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "agent_id": "<string>",
  "variables": {},
  "overrides": {
    "llm": {
      "provider": "<string>",
      "model": "<string>"
    },
    "first_message": "<string>"
  }
}
'

{
  "id": "<string>",
  "server_url": "<string>",
  "participant_token": "<string>"
}