The command you’re trying is old. The documentation site you’re checking is in-line with beta (0.6.5) , while command you’re trying to execute is nightly (0.7.0-rc7). Use github doco for the right version of syntax based on the version you’re running
I can find a fragment id by looking at the log messages(jcli rest v0 message logs -h http://127.0.0.1:3100/api ), but I’m not sure where to find the output-index?