This isnt an answer to your specific question but this looks like a measurement of the business hosts in a production, the number of Txns and the average time. Might this be already satisified by the Activity Monitor Dashboard. This dashboard is supported by the data in the tables Ens_Activity.*
for the example you provided given that the methods invoked by the <routes> are classmethod I commonly do something along the lines of
<Route Url="/error/list" Method="GET" Call="GetErrors" />
ClassMethod GetErrors(pStartTime As %UTC = "", pEndTime As %UTC = "") As %Status
{
#DIM tSC As %Status = $$$OK
#DIM eException As %Exception.AbstractException
#DIM %request As %CSP.Request
Try {
Set:$Get(%response)'="" %response.ContentType="application/json"
If $Get(%request) {
Set tStartDate = $Get(%request.Data("StartTime",1))
Set tStopDate = $Get(%request.Data("EndTime",1))
}
Else {
#;If they are defined in the parameter list
If pStartTime'="" Set tStartDate=pStartTime
If pEndTime'="" Set tStopDate=pEndTime
}
You might find some success looking at the tables/sqlprocs found in the %SQL* schemas