FieldDescribe

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "#/components/schemas/FieldDescribe",
  "title": "FieldDescribe",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "The API name of the field"
    },
    "label": {
      "type": "string",
      "description": "The display label"
    },
    "type": {
      "type": "string",
      "description": "The Salesforce field type (string, boolean, int, double, date, datetime, id, reference, picklist, textarea, etc.)"
    },
    "length": {
      "type": "integer",
      "description": "Maximum length for string fields"
    },
    "nillable": {
      "type": "boolean",
      "description": "Whether the field can be null"
    },
    "createable": {
      "type": "boolean"
    },
    "updateable": {
      "type": "boolean"
    },
    "custom": {
      "type": "boolean"
    },
    "picklistValues": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "value": {
            "type": "string"
          },
          "label": {
            "type": "string"
          },
          "active": {
            "type": "boolean"
          },
          "defaultValue": {
            "type": "boolean"
          }
        }
      }
    },
    "referenceTo": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "description": "For reference fields, the SObject types this field can point to"
    },
    "relationshipName": {
      "type": [
        "string",
        "null"
      ],
      "description": "The name of the relationship for reference fields"
    }
  }
}