Agent Link Parameter - Where can I get these parameters?

I have found other similar information such as assetDescriptors, assetInfos, metaItemDescriptors and valueDescriptors through the HTTP APIs (Pic 1), but I cannot find any APIs related to the additional parameters Agent link (Pic 2). I mean how does the Web know these parameters to show up? Get it from the server or create the client side? Thanks for help!

Pic 1.

Pic 2. Add “Agent Link” to an Asset, then click Add Parameter.