I like the simple plain text signing format for the API calls. For example: <a href="https://sum.golang.org/lookup/go.etcd.io/etcd@v0.4.0" rel="nofollow">https://sum.golang.org/lookup/go.etcd.io/etcd@v0.4.0</a><p>Is signed with:<p><pre><code> — sum.golang.org Az3grobHchAJWrV4M34o1kLnZV4vrGSfFA+2Q9VClbmWqBjsnN4GzK1xB1RaYGSo0jIjWH9GDcR3Tja5sadw2ESoKwg=
</code></pre>
The format is documented here: <a href="https://godoc.org/golang.org/x/mod/sumdb/note" rel="nofollow">https://godoc.org/golang.org/x/mod/sumdb/note</a>