A resource-only deposit is a way of adding or updating certain elements in an existing metadata deposit without having to do a full metadata redeposit. Resource-only deposits use the resource-only section of the schema (with the exception of stand-alone components which use the main deposit section of the schema).
Whether you use a helper tool or submit your own XML to Crossref, you may find a resource-only deposit useful for adding the following:
Uploading resource-only deposits
Resource-only deposits may only be submitted for existing Crossref DOIs. Deposits using the resource-only section of the schema must be uploaded with type
doDOICitUpload for HTTPS POST, or DOI Resources if you are using the admin tool.