Well the meta get_status route should be a way to get route status.
esi-assets endpoint has disappeared again, disappeared both from the OpenAPI spec and from the get_status route (lol).
Compounding the problem of being down, when it goes down, it blackholes everything related to it so we cannot even monitor the status of it and also blocked from development if we happen to be generating a stub at that time.
In PowerShell you can do the following (I am using Linux powershell so grep is easy to use, typically on PowerShell one filters objects using Where-Object and strings using Select-String cmdlets).
PS> Invoke-RestMethod https://esi.evetech.net/status.json?version=latest |Format-Table |grep -i assets
Meta routes are here EVE Swagger Interface