I apologize if this is impossible to debug, but this has been happening on my Mac with macOS Sierra 10.12.2 installed since a few weeks and I thought I'd give it a shot.
Basically, a metadata.json file gets automagically created on my desktop. I delete it. It appears again after a while. GOTO 1.
Google gets a bit mixed up when I search for answers.
So, how would I begin to find out which app is the culprit?
Edit: this is the file contents (duh!):
{"name":"Desktop","modificationTime":1484074718317,"categories":[]}
I run the suggested command and I got this:
501 788 Sketch -1 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 356 bird 25 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
0 76 mds 16 /Users/ignacio/Desktop/metadata.json
501 788 Sketch 29 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 22 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 22 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
0 76 mds 16 /Users/ignacio/Desktop/metadata.json
501 720 mdworker 10 /Users/ignacio/Desktop/metadata.json
dtrace: 2154 dynamic variable drops with non-empty dirty list
501 908 Sketch -1 /Users/ignacio/Desktop/metadata.json
501 356 bird 25 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 908 Sketch 18 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
0 76 mds 16 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
0 76 mds 16 /Users/ignacio/Desktop/metadata.json
501 718 mdworker 10 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 347 Finder 13 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
501 893 quicklookd 21 /Users/ignacio/Desktop/metadata.json
Best Answer
You can use opensnoop to see what app writes to that location.
Source: Disable OS X El Capitan Rootless and permit write actions to System Integrity Protection locations