  Blockchains are gaining momentum due to the interest of industries and people
in \emph{decentralized applications} (Dapps), particularly in those for trading
assets through digital certificates secured on blockchain, called tokens. As a
consequence, providing a clear unambiguous description of any activities
carried out on blockchains has become crucial, and we feel the urgency to
achieve that description at least for trading. This paper reports on how to
leverage the \emph{Ontology for Agents, Systems, and Integration of Services}
("\ONT{}") as a general means for the semantic representation of smart
contracts stored on blockchain as software agents. Special attention is paid to
non-fungible tokens (NFTs), whose management through the ERC721 standard is
presented as a case study.
