All the My Messages API calls seem to be related to sellers communicating with buyers, but what about buyers replying to a message from the seller? When we use the credentials of the buyer to reply to a message from the seller using AddMemberMessageRTQ we get the error "Only the seller who listed the item can retrieve the message for the item or can respond to a question about the item." Is there a different API call we can use for this? Thanks for any help with this problem.
No we don't have anything for that. As you noticed all of our API's are pretty much seller based. Since buying is a manual process already, I think the API teams just assumed everything should be manual for them. But this way of thinking is changing in the future, and we will have new sets of API's coming out within a few years.