{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://gradethread.com/grade-standard.schema.json",
  "title": "GradeThread Grade Field",
  "description": "The GradeThread Standard v1.0 — an open, versioned specification for the machine-readable GradeThread condition grade field. Attach this to a listing, Product, or Offer so the grade is comparable and citable the way card listings cite a PSA grade. This describes the open standard only; it makes no claim that any third party has adopted it. Spec: https://gradethread.com/grading-standard. Licensed CC BY 4.0.",
  "type": "object",
  "required": ["standard", "version", "grade", "scaleMin", "scaleMax"],
  "additionalProperties": false,
  "properties": {
    "standard": {
      "const": "gradethread",
      "description": "Fixed discriminator identifying the GradeThread Standard."
    },
    "version": {
      "type": "string",
      "const": "1.0",
      "description": "Spec version. Bumped only on a breaking change to this shape."
    },
    "grade": {
      "type": "number",
      "minimum": 1,
      "maximum": 10,
      "description": "The overall condition grade on the GradeThread 1.0–10.0 scale, in half-point increments."
    },
    "scaleMin": {
      "const": 1,
      "description": "Lowest possible grade on the scale."
    },
    "scaleMax": {
      "const": 10,
      "description": "Highest possible grade on the scale."
    },
    "tier": {
      "type": ["string", "null"],
      "description": "Named tier the grade maps to (NWT, NWOT, Excellent, Very Good, Good, Fair, Poor).",
      "enum": ["NWT", "NWOT", "Excellent", "Very Good", "Good", "Fair", "Poor", null]
    },
    "cert": {
      "type": ["string", "null"],
      "description": "PSA-style certificate number, e.g. \"GT-ABC123\"."
    },
    "certUrl": {
      "type": ["string", "null"],
      "format": "uri",
      "description": "Public certificate URL a buyer can open to verify the grade."
    },
    "spec": {
      "type": "string",
      "format": "uri",
      "description": "Canonical URL of the published specification."
    }
  },
  "examples": [
    {
      "standard": "gradethread",
      "version": "1.0",
      "grade": 8,
      "scaleMin": 1,
      "scaleMax": 10,
      "tier": "Excellent",
      "cert": "GT-ABC123",
      "certUrl": "https://gradethread.com/cert/EXAMPLE",
      "spec": "https://gradethread.com/grading-standard"
    }
  ]
}