Workspace-level surge protection settable via API?

there is no public api available today to configure workspace level surge protection or workspace availability settings and it is not just a documentation gap. As of now, the workspace level capacity controls introduced in preview (Available/Mission critical/blocked) are UI only. Neither the PBI REST APIs nor the Fabric admin APIs expose endpoints to read or set these workspace capacity options programmatically. MS has not published a timeline for API support yet, but based on past patterns (capacity admin features, tenant settings), API enablement typically comes after GA, not during preview. If you have a large no of workspaces, manual configuration or internal automation via UI scripting is the only option today. Expect proper API support only once this feature exits preview and is operationally live.

Hello KimY 

There are no public APIs available as of today, however there's an active Idea related to this, which requests to put capacity usage limit more granular, at workspace item level. 

workspace capacity usage limit configuration - Microsoft Fabric Community

If you'd like to have REST API for for Workspace Surge Protection, I suggest you raise it as an Idea. Click on Ideas in the above menu and submit an Idea on this. I am happy to vote for this, as I think it'd be good to have this at the same time it comes out as a GA capability.