const options = {
  method: 'GET',
  headers: {'X-Spree-Seller-Id': '<x-spree-seller-id>', Authorization: 'Bearer <token>'}
};

fetch('http://{defaultHost}/api/v3/seller/delivery_methods/rule_types', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

curl --request GET \
  --url http://{defaultHost}/api/v3/seller/delivery_methods/rule_types \
  --header 'Authorization: Bearer <token>' \
  --header 'X-Spree-Seller-Id: <x-spree-seller-id>'

{
  "data": [
    {
      "type": "item_total_rule",
      "name": "Item total",
      "description": "Limits the delivery method to carts within an item total range",
      "preference_schema": [
        {
          "key": "minimum_amount",
          "type": "decimal",
          "default": null
        },
        {
          "key": "maximum_amount",
          "type": "decimal",
          "default": null
        }
      ]
    },
    {
      "type": "weight_rule",
      "name": "Weight",
      "description": "Limits the delivery method to packages within a weight range",
      "preference_schema": [
        {
          "key": "minimum_weight",
          "type": "decimal",
          "default": null
        },
        {
          "key": "maximum_weight",
          "type": "decimal",
          "default": null
        }
      ]
    },
    {
      "type": "volume_rule",
      "name": "Volume",
      "description": "Limits the delivery method to shipments within a volume range, in cubic meters",
      "preference_schema": [
        {
          "key": "minimum_volume",
          "type": "decimal",
          "default": null
        },
        {
          "key": "maximum_volume",
          "type": "decimal",
          "default": null
        }
      ]
    },
    {
      "type": "company_rule",
      "name": "Company",
      "description": "Offers the delivery method only to orders placed for a company, or only to orders that are not",
      "preference_schema": [
        {
          "key": "company_orders_only",
          "type": "boolean",
          "default": true
        }
      ]
    }
  ]
}