This is exactly what snow-fort defines:
http://snow-fort.org/doc/spec/
[...]
It may not have everything you want but is a simple and extensible
format, and the site has been in active use since 2015.
The Snow-Fort format is included in the survey at
<https://github.com/pre-srfi/scheme-metadata-files>. Most existing
Scheme package managers use a metadata format similar to it. They just
use slightly different field names and syntax to encode similar information.
This means that agreeing on a common format supported by all the package
managers is a tractable problem. I intend to pursue it by writing
scripts to download the existing package indexes, and convert them to
the proposed common format. When all the existing information can be
losslessly converted, that proves the new format is good enough.
