json deserialized object has ISError Property by default?

In the code below, using prototype library, the Ajax.request returns a set of data which i can see is populated in the var response object.

There is alot of data in the var response object, but the IsError and AppItems object are undefined.

Is there supposed to be an ISError property by default, or would this have to be defined in the AJAX data which is returned?

[CODE]new Ajax.Request(url, {
method: ‘get’,
onSuccess: function(transport) {
// Parse out serialized response
var response = transport.responseText.evalJSON(); // this has many properties but, not IsError
if (response.IsError) {
setResultMessage(response.Message, response.IsError);
return;
}
else
{
// Always start at first page
currentPage = 1;

// Fill the search results
fillSearchResults(resultsTable, response.AppItems); //this response.AppItems is never defined either
return;
}
}
}
); [/CODE]

Thank you for input.

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