$ curl -H "Accept: application/json" -s \
    'http://127.0.0.1:4433/self-service/login/flows?id=a2d6e166-5153-42a6-8943-ef99eba8ab2e' \
    | jq -r '.ui.messages'

[
  {
    "id": 4000006,
    "text": "The provided credentials are invalid, check for spelling mistakes in your password or username, email address, or phone number.",
    "type": "error",
    "context": {}
  }
]
