I concur with Haruhiko about the why, but assuming you have a valid reason for needing this information one way to retrieve it would be using APMSQL or the SQL REST API. See the documentation for the "APMSQL Recipes" (https://docops.ca.com/ca-apm/10-7/en/integrating/apmsql-cookbook/apmsql-recipes)
A query that might come close to what you are looking for is just retrieving every metric path that was reported the last 20 seconds:
SELECT distinct agent_host, agent_process, agent_name, metric_path
WHERE frequency = 15000
AND ts BETWEEN Timestampadd(sql_tsi_second, -20, Now()) AND Now()
ORDER BY agent_host, agent_process, agent_name DESC
Be aware that this can be a huge query with a huge result set depending on the number of agents and their metric configuration reporting to your cluster, so take into account the resources needed for running this.