A collaborator sent me an abstract he's submitting to a conference, listing me as a co-author (middle position, implying not a major contribution). It's for a conference presentation, not a manuscript, and it will not be published in e.g. a supplement or anything like that.
I've spent a fair bit of time with him discussing and planning the project, I'm listed as a co-PI on the grant, and I expect to provide important contributions later in the project, but at this point I haven't specifically contributed, in any hands-on way, to the exact work described in the abstract.
I thanked him, made some minor suggestions about the abstract, and suggested that he didn't need to include me as I hadn't contributed enough yet. He replied saying that he was happy to include me.
The work is fine and I have no concerns or reservations about it. We're roughly at equal career stages and neither of us is new, so neither of us is looking for extra prestige etc. If we cared about fine balances, I'm probably helping him more than he's helping me in the project, but I'm happy to do it. I have made significant contributions to the overall experimental design and planning, and it's not ridiculous to be an author, but it is for a smaller contribution than I consider authorship-worthy.
Should I continue to battle to be taken off the authorship?