In section "2.6.2. Example file" of the AppStream documentation this example id is given:

<id>org.gnome.gedit-code-assistance</id>

Which gives a bad example though, as section "2.1.3. XML Specification" has a note "Escaping characters in the component ID" which recommends "to replace any hyphens in the ID with underscores".

If being inspired by the example only, then appstreamcli complaining about such hyphens, results in developers rolling theirs eyes unwantedly, which can be harmful ;)