Oh. Now I understand.
Although I haven’t done it, you can get to pfSense metrics with SNMP:
https://www.youtube.com/watch?v=CKPbIeiJ2AQ
https://community.home-assistant.io/t/pfsense-stat-monitor/61070/34
https://community.home-assistant.io/t/device-tracker-with-pfsense-router/22231/75
https://docs.netgate.com/pfsense/en/latest/services/snmp.html
https://www.home-assistant.io/integrations/snmp/
As an aside, there is some Netgate development activity related to an API.