Yes, it's easy, but you would need to use a different API. Instead of:
sendassetfrom <from> <to> <asset> <qty>
Use:
sendwithdatafrom <from> <to> '{"<asset>":<qty>}' '{"json":{"i":[1,2],"j":"yes"}}'
This assumes you are using the multichain-cli command line and want to add JSON metadata outside of a stream. See this for other options:
https://www.multichain.com/developers/json-rpc-api/#metadata