LLM-initiated purchases probably rack up chargebacks, support calls, etc for mistakes the LLM makes. I'm not surprised they want to limit it.
More likely, they want to be the exclusive provider of LLMs that can purchase off of eBay, or at least charge for API access.
Right -- this seems more of a protective measure than something they will proactively enforce.
If you have a well-behaved agent that uses a browser to buy on eBay, I doubt that will cause issues. But if it leads to issues, they can point to that clause instead of having to help repair the issues caused by someone else's software.
I might be out of the loop, but are agents actually out there buying stuff from "unwilling" vendors at any significant scale? I thought that was still mostly limited to opt-in partnerships with retailers. Still, eBay might be anticipating the issues you mentioned and trying to get ahead of them.