Every host the repository claims support for has a working install path
A README that names a host it has shipped nothing for sends a reader to a command that fails. Hosts read different manifests, so support is a file at a path, not a sentence.
Observable check
for every host named in README.md or in the install documentation it links to, either the manifest that host reads is committed at the path the host reads it from, or a documented install command exists that needs no manifest; and no host is named that has neither. oss-skill lists the manifest path each host reads, and every manifest it also accepts, in references/hosts.md in its own installed directory: read it there rather than from the host's docs. A host that accepts another host's manifest passes on that file, as Codex does with a Claude-compatible .claude-plugin/plugin.json.
Where this comes from
No upstream source. This is oss-kit's own position, and the argument for it is below.
The Agent Skills specification defines one skill layout and says nothing about installing a repository of skills into any particular host. Observed: hosts read different manifests from different paths, so naming a host in a README proves only that somebody typed the name, and a reader following it reaches a command that fails. Retire this rule if one manifest format is ever read by every host.