curl -X POST https://www.openindex.ai/api/chat \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer <your OpenIndex API key>' \
  -d '{"chatId": <existing chatId or empty to start a new conversation>, \
    "agentId": "d9H4LWDyFA6VmXvJbfI9", \
    "message": "Hello, how are you?"}'