Summary
There is a way to check the available counters for Oracle 10G application server monitor using the DB directly
Question
How to check the available counters for Oracle 10g application server monitor
Answer
Available counters for Oracle 10g Application server monitor can be verified using this URL:
http://<OracleHostName>:<Port>/dmsoc4j/Spy?format=xml
In that XML are all the available counters for that specific database: