The Aqara Open API is a cloud-based REST API. It is not local to the hub. It uses HTTP requests over the internet to communicate with the Aqara Cloud, which then remotely interacts with your setup.
If you have an FP2 and/or a G3 Camera Hub, have a look at my post here: [Tutorial] Integrating Aqara G3 into Home Assistant with Video + PTZ
The author of the AqaraPOST Home Assistant integration uses an older version of the Aqara Open API (V1) together with Node-RED Companion.
You can find information about the Aqara Open API here: https://opendoc.aqara.cn/en/