Well there is a rule in Germany, almost a law, that employers have to write true and benevolent job references for employees that left the company.
Imagine you were the HR of a self-service-store looking for a sales clerk and an applicant would send you a reference of(by) another self-service-store recruiter, reading:
“Mr/Mrs X fully adopted the rules of self-service.”
Would you or would you not hire the candidate?
Hi Michael, thanks a lot for your interesting question - you’ve brought up a topic that relevant in many countries which is why I would be interested to hear how our users respond. In the meantime, if you asked me, I would probably install a system similar to the one operated by Amazon Go.
lol Torsten, you know I am a countryside habitant (“Landei” in German 
). Thus I am not this familar with Amazon Go. But I imagine you mean this sort of malls where you can watch products under a bulletproof glass box and make your order. Well that´s a smart idea 
I agree that you should try to write an honest reference for a former employee. The secret of a good reference is what you don’t say about someone. A future employer can as we say, read between the lines.
Hi Alan. Yes, and what´s more: you need to know the phrases. Here are some of phrases that reads pretty good to not experienced people:
Mrs./Mr. X regularly came on the dot.
Mrs./Mr. X always has been eager on doing her/his best job performance.
Mrs./Mr. X usually provided for a good atmosphere on the job.
Mrs./Mr. X always received the goals set to our satifaction / complete satisfaction / utter satisfaction.
We wish Mrs./Mr. X all the best (or good luck?) for/in the furture.
Would be glad to know some more. 