Mass Market ERC721 extension for Shops

This document describes changes to the ERC721 standard, altering specifically the optional Metadata extension expressed as JSON Schema. The changes are specified for use with the Mass Market protocol.

For more context, see: masslbs/Tennessine#640

Schema

The complete JSON schema is available in schema.json. Key extensions to the ERC721 metadata standard include:

{
    "title": "Asset Metadata",
    "type": "object",
    "properties": {
        "name": {
            "type": "string",
            "description": "Identifies the asset to which this NFT represents"
        },
        "description": {
            "type": "string",
            "description": "Describes the asset to which this NFT represents"
        },
        "image": {
            "type": "string",
            "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive."
        },
+       "brief": {
+           "type": "string",
+           "description": "A shorter description of the the asset to which this NFT represents, recommended to 100-120 characters.",
+           "minLength": 100,
+           "maxLength": 120
+       },
+       "background": {
+           "type": "string",
+           "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and a rectangular aspect ratio of 1.91:1."
+       },
+       "discoverable": {
+           "type": "boolean",
+           "description": "Controls whether the referenced asset is allowed to be displayed through discovery mechanisms."
+       },
+       "paymentAddresses": {
+           "type": "array",
+           "description": "An array of ethereum addresses which the merchant accepts payments to",
+           "items": {
+                "$ref": "#/$defs/address"
+           }
+       },
+       "acceptedCurrencies": {
+           "type": "array",
+           "description": "An array of ethereum tokens which the merchant accepts as payments",
+           "items": {
+               "$ref": "#/$defs/address"
+           }
+       },
+       "pricingCurrency": {
+           "type": "object",
+           "description": "The currency which the listing in the shop are priced",
+           "properties": {
+               "address": { "$ref": "#/$defs/address" },
+               "chainId": { "type": "number" }
+           },
+           "required": ["address", "chainId"]
+       }
    },
+   "required": ["pricingCurrency", "acceptedCurrencies", "paymentAddresses", "name"]
}

Field Descriptions

Legend with respect to interpreting the above schema for Mass Market purposes, given that the underlying NFT represents a Mass Market Shop:

• name - the shop profile name. Its recommended length is 40 characters. Required.
• description - the full shop profile description.
• image - the shop profile image. The profile image should be a square 1:1 format in the range of 320px x 320px to 1080px x 1080px. It will be rendered with a circular passe-partout in the Mass Market interface.
• brief - a shorter shop description, displayed on aggregated shop discovery pages. Must be 100-120 characters. If the string is in excess of 120 characters, the 121th character onward will be trimmed in the Mass Market interface.
• background - the shop background image, displayed on aggregated shop discovery pages. The background image should be a rectangular 1.91:1 ratio in the range of 320px x 168px to 1080px x 567px.
• discoverable - controls whether the shop is displayed on discovery pages.
• paymentAddresses - array of Ethereum addresses where the shop accepts payments. Required.
• acceptedCurrencies - array of ERC20 token addresses that the shop accepts as payment. Required.
• pricingCurrency - the primary currency used for pricing items in the shop, with contract address and chain ID. Required.

Development

This project uses Nix for development environment management.

Setup

# Enter development environment (requires direnv or manual nix develop)
nix develop

Testing

Validate the JSON schema:

# Run schema validation
just test

# Or directly
jv ./schema.json