SageX3 Rest API Web Services - how to get contract schema xsd?

Hello Community,

Using Rest API Web Services in Sage X3 how can I get a contract schema definition XSD?

The goal here is to get a list of available resources.

SDATA documentation (http://sage.github.io/SData-2.0/pages/core/0401/ ) says it is possible via this request

GET /sdata/myApp/myContract/-/$schema

I tried the following request and it failed

10.0.3.137:8124/.../$schema

Response
{
    "$diagnoses": [
        {
            "$severity": "error",
            "$message": "bad request",
            "$stackTrace": "bad request"
        }
    ]
}
At the same time, if I query a resource directly, it always works. For example, this query works.
10.0.3.137:8124/.../BPCUSTOMER
How can I get the Contract Schema definition? How do I get a list of available resources (classes) my app can query?
Thank you a lot. I am really stuck at this task...
Nick