curl --request POST \
  --url https://api.example.com/api/v2/projects/{project_id}/completions/{completion_id} \
  --header 'Content-Type: application/json' \
  --data '
{
  "new_messages": [
    {
      "content": "<string>",
      "role": "system"
    }
  ],
  "eval_results": {}
}
'

{
  "completion_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
}