{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Imagery Source List",
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "attribution": {
        "type": "object",
        "properties": {
          "required": {
            "type": "boolean"
          },
          "text": {
            "type": "string"
          },
          "url": {
            "type": "string",
            "format": "uri"
          }
        },
        "required": ["required", "text", "url"]
      },
      "description": {
        "type": "string"
      },
      "extent": {
        "type": "object",
        "properties": {
          "max_zoom": {
            "type": "integer"
          },
          "polygon": {
            "type": "array",
            "description": "List of linear rings. Each ring is an array of [lon, lat] pairs. Rings must be closed (first and last coordinate equal).",
            "minItems": 1,
            "items": {
              "type": "array",
              "minItems": 4,
              "items": {
                "type": "array",
                "minItems": 2,
                "maxItems": 2,
                "items": {
                  "type": "number"
                }
              }
            }
          }
        },
        "required": ["max_zoom", "polygon"]
      },
      "icon": {
        "type": "string",
        "format": "uri"
      },
      "id": {
        "type": "string"
      },
      "name": {
        "type": "string"
      },
      "type": {
        "type": "string",
        "enum": ["tms", "wmts", "xyz"]
      },
      "url": {
        "type": "string"
      }
    },
    "required": [
      "attribution",
      "description",
      "extent",
      "icon",
      "id",
      "name",
      "type",
      "url"
    ]
  }
}