Hi atassani,
There is a method for monitoring the CA API Gateway with SNMP. I have attached the guide we published (it's a bit long in the tooth but it still applies to the product). You'll want to pay extra attention to chapter ten which talks about integrating the CA API Gateway with Nagios.
Please review that document and let me know if you have any questions around it.
Sincerely,
Dustin Dauncey
Support Engineer, Global Customer Success
Email: API-Support@ca.com
Phone: +1 800 225 5224
Outside of North America - ca.com/us/worldwide.aspx
CA API Management Community: ca.com/talkapi