Validators (e.g. the Nu Html Checker) often report errors with references to the specification requirement that was violated. To get a good user experience and protect against checking unspecified behavior, I think ocitools checks should be setup to link to the relevant spec wording for any check they perform. For example, a bundle with non-UTF-8 JSON would fail with a reference to this. If this sounds like a reasonable policy, we should write it up in the README or a CONTRIBUTING.md and open issues/PRs for adjusting any existing checks.