Hello @Evgeny Shvarov 
I directly use %DymaicObject and %DynamicArray and its methods depends on the response type (array or object) to set the values into the JSON response and I use %WriteResponse to write that response to the API call

 Class sample.Impl Extends  %REST.Impl {
 
 ClassMethod GetAllPersons() As %Stream.Object
{
    d ..%SetContentType("application/json")
    set res =  {"name":"test" 
    do ..%SetStatusCode(200)
    do ..%WriteResponse(res)
    q 1
    
}

Mixed of stream data types and other datas then creates a stream and convert into DynamicObject if required and write that response.

Right, It worked! The issue was a mismatch in the super server port. 

Hello @Vitaliy Serdtsev,

I executed the routine invocation commands in native python script.