curl --request POST \
  --url 'https://api.nsr.stateset.com/api/v1/beliefs' \
  --header 'X-API-Key: YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
  "confidence": 0.95,
  "proposition": "socrates_is_mortal",
  "source": "observation"
}'

{
  "belief_interval": [
    {}
  ],
  "confidence": 1,
  "is_certain": true,
  "is_rejected": true,
  "proposition": "string",
  "uncertainty": 1
}