Are you having issues when adding one in game? If so then you would use [add "tool" "resource" charges". So lets say you wanted to add a runic sewing kit for spined leather with 100 charges, then you would do [add runicsewingkit spinedleather 100
Or you can't find the runic tool files? If so they are located in /scripts/items/tools folder. RunicDovetailSaw.cs, RunicFletcherTool.cs, RunicHammer.cs, RunicMalletAndChisel.cs, and RunicSewingKit.cs are the runic tool files.