https://api.gog.com/products/1207659001?expand=downloads,expanded_dlcs,description That mostly worked for me.
The exception seems to be cover image and boxart, plus publisher, and maybe some other stuff.
I was able to get all the browser type download links, which I then queried using gogcli.exe, and I got a checksum and bytes plus file name for each of the installer files, but bytes and file names failed to be returned for the five Extras files, until I used curl to query each file directly via the true download link.
I've come across several games in the last few weeks that return bad metadata for some files. In most cases, it is just one or more of the Extras files.