[galaxy-user] When to use metadata or dataset.blurb?

So I wanted to add in the number of sequences in a file, which is something that is often requested. My initial thought was to add a tool, which I could do, but then I thought that this was metadata that should probably be added to any record based class. So I then thought that I would find the code that set up the file size information in the history column and copy that, but looking at the source, that goes in the blurb (e.g. sequence.Fasta). So here are my questions: * how can a user see the metadata, as this is distinct to the blurb/peek? * why isn't the file size implemented as a piece of metadata? thanks, James