What does a missing value mean?

The API uses null when a value is not known. Zero is a known value of zero. They are not the same.

dataStatus.missingFields lists each field that is not known. dataStatus.state tells you the broad state. notes gives short causes. scoreComplete says if all score parts were known. comparable says if the headline price check is fit to compare.

A price can be fit to compare while the Score has missing parts. Check the named field to see what is still needed.

Sample

{
  "premiumPct": null,
  "comparable": false,
  "dataStatus": {
    "state": "unavailable",
    "quoteTs": null,
    "poolTs": 1789410000,
    "computedTs": 1789410006,
    "scoreComplete": false,
    "notes": ["Stock quote is not available."],
    "missingFields": ["refPrice", "premiumPct"]
  }
}

Do not draw premiumPct: null at the zero line.

Next

Read the known limits.