Did you take a look at the SYS.ApplicationError class? It has methods and class queries for reading the Application Error Log.

For example, to get the dates when errors were logged for a particular namespace TEST, you can use

do ##class(%ResultSet).RunQuery("SYS.ApplicationError", "DateList", "TEST")  

Or to manually parse the results, you can use

set $NAMESPACE = "%SYS"
set resultSet = ##class(%Library.ResultSet).%New("SYS.ApplicationError:DateList")
set status = resultSet.%Execute("TEST")

You can use the $THIS special variable. For example:

runTag(parameter)
    set t = $THIS
    do t.Data.Insert("abc")
    w t.Data.GetAt(1)
    q