ERC-721 composition proposal would expose mint-time asset declarations

A new Ethereum Magicians discussion proposes a way for wallets, indexers and marketplaces to read the assets declared when an NFT was minted. Posted on November 2, the ERC-721 Composition Extension describes a container for each token and an interface for reading its declared contents. It is a proposal under discussion, with a public repository and standards pull request described as future steps.

The distinction is between a declaration and a current balance. Under the proposed rules, compositionOf(tokenId) would return a list of native assets or ERC-20 tokens and their declared amounts. The list would be fixed at mint. Assets sent to the container later would be surplus, so a larger balance would not change that declaration.

A second function, compositionAccountOf(tokenId), would identify the container, its interface type and the data needed to check its identity. The proposed CompositionDeclared event would announce the same information once for each token at mint, including tokens minted in a batch. Both functions would continue returning their original data after the token was burned.

The proposed container rules would prohibit assets leaving while the NFT exists. After a burn, withdrawal authority would follow the address recorded by the separate ERC-8423 burn-record interface. Minting, burning, asset prices, valuations, oracles and yield are outside the proposed composition interface.

The discussion has already produced changes the author intends to add to a specification. In a November 2 reply, the author agreed to require the container contract to exist by the end of the minting transaction and to make the implementation restrictions more explicit. The author also proposed rejecting transfers to any container declared by the same collection, rather than only a token's own container.

For developers, the immediate development is a concrete interface to examine and comment on. The thread does not establish a deployed standard or independently tested implementation, and declared contents should not be read as a valuation.