Using the $protoype requests I can see that the representations have instanceUrl property, however I am unable to use these:

"$baseUrl": "">servername:8124/.../TESTI",
"$baseType": "application/json;vnd.sage=syracuse;vnd.sage.syracuse.representation=x3.erp.TESTI",
"$prototype": "{$baseUrl}/$prototype('{$representation}.$thumb')",
"$representation": "QLYCRD",
"$repUrl": "{$baseUrl}/QLYCRD",
"$instanceUrl": "{$repUrl}/QLC",
"$url": "{$baseUrl}/QLYCRD('{$key}')?representation=QLYCRD.$details",
"$key": "{QLYCRD}",

I can use the $url with my rest client and get results, but I cannot use the instance URL.

http://servername:8124/mobile1/x3/erp/TESTI/QLYCRD/QLC

I receive "The syntax of the query is faulty". What is the instanceUrl for and how do you use it?