A yet another workaround for non-obvious caveat of using %JSON.Adapter  and JSON transport around persistent data is a necessity to add an ID related property to your persistent class, like PersonId in this case:

Property PersonId As %Integer [ Calculated, SqlComputeCode = { set {*}={%%ID}}, SqlComputed ];

This will allow to export ID of a record in DB automatically.

Same when you do updates with records, you need to remove this PersonId JSON from an update request, .e.g like this:

set personDynObj= {}.%FromJSON(person.Read())

do personDynObj.%Remove("PersonId") // Remove PersonId if it exists, as it is calculated

set sc = personObj.%JSONImport(personDynObj)

set sc = personObj.%Save()

And 3 parameters for the spec class that help: HandleCorsRequest - it is most likely CORS will be needed, applicaton/json to support JSON content and ExposeServerExceptions for debug reasons:

Class shvarov.person.spec Extends %REST.Spec [ ProcedureBlock ]

{

Parameter HandleCorsRequest = 1;
Parameter CONTENTTYPE = "application/json";
Parameter ExposeServerExceptions = 1;
...

also I always add the same _spec GET endpoint to let swagger have a working specification in docker - the default one doesn't work in docker as IRIS default spec one overrides the host variable to one, that doesn't work.

ClassMethod GetSpec() As %DynamicObject
{

set specname=$p(..%ClassName(1),".impl")

Set spec = {}.%FromJSON(##class(%Dictionary.CompiledXData).%OpenId(specname_".spec||OpenAPI").Data)

Set url = $Select(%request.Secure:"https",1:"http") _ "://"_$Get(%request.CgiEnvs("SERVER_NAME")) _ ":" _ $Get(%request.CgiEnvs("SERVER_PORT")) _ %request.Application
Set spec.servers = [{"url" : (url)}]

Quit spec

}