The WMI type provider allows you to query WMI services with strong typing.
To output the results of a WMI query as JSON,
open FSharp.Management
open Newtonsoft.Json
// `Local` is based off of the WMI available at localhost.
type Local = WmiProvider<"localhost">
let data =
[for d in Local.GetDataContext().Win32_DiskDrive -> d.Name, d.Size]
printfn "%A" (JsonConvert.SerializeObject data)