Why is this tool deprecated?
I was specifically asked by a US government agency how they can validate that their OCI containers are properly formatted. They want a repeatable way to attest to the validity of what others give them. A properly formatted OCI container is one condition.
The validation code (oci-image-tool validate) is not hard deprecated, only the image manipulation tools (the other ones) are completely deprecated and should not be used (umoci is the OCI reference implementation of the image-spec that replaces this functionality).
However, the validation code is not being regularly updated (due to a lack of maintainership manpower). We have discussed moving the validation code to umoci but there hasn't been any progress on that topic (umoci uses the oci-tools image validation in all of its tests, so the code can still be used).