Right. Aside from 'files' and 'bytes', the metrics are just the result of running shell commands specified in a config file. In this case it's `jq '.items | len

Right. Aside from 'files' and 'bytes', the metrics are just the result of running shell commands specified in a config file. In this case it's `jq '.items | length' $PARCEL_PATH`, i.e., parse the file and print the length of the attribute named "items". Obviously, that won't catch all potential problems in the file, but it's a low-effort way to catch some.