schema.json

{
  "$schema": "https://json-schema.org/draft/2019-09/schema",
  "$id": "https://json-schema.org/draft/2019-09/output/schema",
  "description": "A schema that validates the minimum requirements for validation output",

  "oneOf": [
    { "$ref": "#/$defs/flag" },
    { "$ref": "#/$defs/basic" },
    { "$ref": "#/$defs/detailed" },
    { "$ref": "#/$defs/verbose" }
  ],
  "$defs": {
    "outputUnit":{
      "properties": {
        "valid": { "type": "boolean" },
        "keywordLocation": {
          "type": "string",
          "format": "uri-reference"
        },
        "absoluteKeywordLocation": {
          "type": "string",
          "format": "uri"
        },
        "instanceLocation": {
          "type": "string",
          "format": "uri-reference"
        },
        "errors": {
          "$ref": "#/$defs/outputUnitArray"
        },
        "annotations": {
          "$ref": "#/$defs/outputUnitArray"
        }
      },
      "required": [ "valid", "keywordLocation", "instanceLocation" ],
      "allOf": [
        {
          "if": {
            "properties": {
              "valid": { "const": false }
            }
          },
          "then": {
            "required": [ "errors" ]
          }
        },
        {
          "if": {
            "anyOf": [
              {
                "properties": {
                  "keywordLocation": {
                    "pattern": "/\\$ref/"
                  }
                }
              },
              {
                "properties": {
                  "keywordLocation": {
                    "pattern": "/\\$recursiveRef/"
                  }
                }
              }
            ]
          },
          "then": {
            "required": [ "absoluteKeywordLocation" ]
          }
        }
      ]
    },
    "outputUnitArray": {
      "type": "array",
      "items": { "$ref": "#/$defs/outputUnit" }
    },
    "flag": {
      "properties": {
        "valid": { "type": "boolean" }
      },
      "required": [ "valid" ]
    },
    "basic": { "$ref": "#/$defs/outputUnit" },
    "detailed": { "$ref": "#/$defs/outputUnit" },
    "verbose": { "$ref": "#/$defs/outputUnit" }
  }
}