A structured tokenData function for on-chain NFTs


A new interface that should implement on-chain NFTs projects, mimicking the current JSON scheme of the IERC721Metadata, but returning the data as a struct.


The ERC721Metadata standard defines a tokenURI(uint256) returns (string memory) that returns a URI containing the metadata for the token.

Most of the projects use centralized (e.g. own servers, AWS) or decentralized (e.g. IPFS) to store this data and consequently returns only a string, e.g. ipfs://....

On-chain projects though have to build on-chain a data uri that is compliant with this interface.

  • it is painful and cost gas to inline all the data and manually jsonify a token
  • it creates a barrier for composability as it is difficult to parse a data:application/json,... on-chain
  • eventually it is a useless op that destructs data without any good reasons: some may think that it’s better to keep standard JSON for data interfacing but it’s not actually the case as a eth_call is not a REST API: even these data uri need to be decoded by eth clients.
  • on the opposite, using such a tokenData would let front end users access directly a typed API. In other words, it’s less work for the on-chain solidity dev and more info for the end user.
  • using the ERC165, there will be no more discussions about “is it on chain or not” ?
  • overall this would incentivize creators to build on-chain to build on top of each others.
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