The recent EU regulation on Markets in Crypto Assets Regulation (MiCA), represents a significant progress in establishing a multi-jurisdiction framework for crypto-assets that will enable the greater participation of consumers in the digital assets industry. One type of token recognized by MiCA is the asset-referenced token, where the value-bearing asset and the provenance metadata supporting the token's claim are located external to the token. We discuss a number of design considerations for the on-chain and off-chain metadata for MiCA's asset-referenced tokens, with the goal of evolving towards a framework where technical standards can be developed for the assets metadata and related smart contracts technology. The EU Data Spaces provides an interesting data management paradigm that could be used for the decentralized registries infrastructure needed to manage the provenance metadata for various assets.