ERC-1046 — tokenURI Interoperability

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ERC-1046: tokenURI for Fungible Tokens

ERC-721 has tokenURI(tokenId) returning per-NFT metadata. ERC-1046 gives fungible tokens (ERC-20) the same affordance: a tokenURI() returning a JSON pointer to the token's metadata (logo, description, decimals override, decimal precision, etc.). Wallets and explorers consume this metadata to render rich token info without per-token integration.

Required Interface

interface IERC1046 {
    function tokenURI() external view returns (string memory);
}

The returned URI typically resolves to a JSON document like:

{
  "name":        "Acme Stable",
  "symbol":      "ACME",
  "decimals":    6,
  "image":       "ipfs://Qm...",
  "description": "Asset-backed stablecoin issued by Acme.",
  "external_url": "https://acme.fi/",
  "tags":        ["stablecoin", "dollar-backed"]
}

Neo Equivalent: NEP-17 + tokenURI() View

Neo NEP-17 doesn't mandate a metadata URI but the convention can be added with a single view method:

[Safe]
public static string TokenURI()
    => (string)Storage.Get(Storage.CurrentContext, new byte[] { Prefix_TokenURI });

ERC-1046 (Ethereum)	Neo Equivalent	Notes
tokenURI() returning string	TokenURI() returning string	Direct port
JSON metadata schema	Same — community-defined extras
Pre-existing on ERC-721	Adopt as convention for NEP-17	New for fungibles

Composition

• ERC-5169 — client script URI. Pair: scriptURI for interactive components, tokenURI for static metadata.
• ERC-7160 — multi-metadata. Tokens with versioned metadata expose multiple URIs.

Migration Notes

For fungible-token wallets / indexers:

1. Add TokenURI() to your NEP-17 contract — set at deploy.
2. Hosting can be IPFS (canonical CID) + HTTPS gateway (fallback).
3. Wallets that already render NFT metadata can re-use the parser for fungible tokens too.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract ERC1046Token {
    string public tokenURI;

    constructor(string memory _tokenURI) {
        tokenURI = _tokenURI;
    }
}

using System;
using System.ComponentModel;
using Neo;
using Neo.SmartContract.Framework;
using Neo.SmartContract.Framework.Attributes;
using Neo.SmartContract.Framework.Native;
using Neo.SmartContract.Framework.Services;

namespace R3E.Examples;

[DisplayName("RichToken")]
[ContractPermission("*", "*")]
[SupportedStandards(NepStandard.Nep17)]
public class RichToken : Nep17Token
{
    public override string Symbol  => "RICH";
    public override byte   Decimals => 8;

    private const byte Prefix_TokenURI = 0xfe;

    [DisplayName("_deploy")]
    public static void Deploy(object data, bool update)
    {
        if (update) return;
        Storage.Put(Storage.CurrentContext, new byte[] { Prefix_TokenURI }, (string)data);
    }

    [Safe]
    public static string TokenURI()
        => (string)Storage.Get(Storage.CurrentContext, new byte[] { Prefix_TokenURI });
}