Hi Miroslav,
no, we deliberately don’t expose card IDs on demand – neither in the UI nor via the API.
You can sync member cards with another system by adding a webhook and listening for memberKey events. But we’ll never let anyone query a specific member’s key – for the same reason that you can’t ask for a member’s password.
But the good news is the new APIs that we’re adding for the Octoprint integration will also be perfect for what you want to do.
Simply read any card and use the new endpoint to ask Fabman whether it’s valid. It will tell you they key’s member (if known) and whether they are allowed to turn on the coffee machine.
Apart from being more secure, this has the benefit of logging whenever someone uses the coffee machine. So you can even charge for making coffee, if you want.