They look around for people susceptible to that kind of message and then DM them and try to convince them to go through with it, see the case of the people trying to kidnap the Michigan governor. There were like 2 actual chuds and 6 feds with them egging them on. ALAB podcast had a good episode on it. That said, i'd guess they probably dont bother with trying to get people to steal from their job, unless your part of an org or something and they want some pretext to investigate you. The spy cops thing in the UK also has some examples of what undercover cops do. You might be able to pull some examples of actual fed posts from court cases, but that sounds like too much work.