The FMS library (will) support the lookup of a manifest entry based on an entry name and downloading the artifact(s) referenced in the manifest entry.
[This lib will be a work in progress for Q2, 2021.]
When working on FMS lib, consider using:
$ fx set [...] --with //src/developer/ffx/lib/fms:tests
Unit tests can be run with:
$ fx test fms_lib_test