curl --request POST \
  --url https://api.opper.ai/v3/compat/v1/messages/count_tokens \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "max_tokens": 123,
  "messages": [
    {
      "content": "<unknown>",
      "role": "<string>"
    }
  ],
  "model": "<string>"
}
'

{
  "input_tokens": 123
}