Set Metadata Note before rendering

I am distributing an animation by pointing multiple computers to a shared directory with the ‘file placeholders’ option enabled (PNGs if it matters). I have found this to be a very straightforward approach to distributing the rendering of an animation. However, I would like to collect some performance statistics, namely which machines render which frames so that I can track their distribution and/or spread across time (the cluster is very heterogenous, some machine being much more powerful than others, so the performance distribution would be interesting to see).

An obvious solution is to inject a per-machine tag into the metadata and pull it out later for aggregated statistics. This is easy to do manually, by opening the file in Blender on each machine and editing the Metadata Note field, and I’ve done this a couple times. But I would love to automate both rendering and editing of this tag so that I can kick the process off from the command line without even launching the GUI.

I dug through bpy in the console via tab completions and couldn’t find a place to set the metadata, even though just about every other property under the sun is up for grabs. I don’t know how I’ve overlooked it, but I also can’t believe it’s nearly the only property that isn’t available through the API.

Any ideas?

Thanks a bunch.