[galaxy-dev] Set metadata from within the tool

Hi everyone, How can I set dataset's metadata from within the tool? For example: From the command tag (in the xml tool specification) i call myscript.sh: <command> myscript.sh -input=$input -output=$output </command> My script.sh produce a value that i want to store as metadata of $input. I've checked the tool config syntax http://wiki.g2.bx.psu.edu/Admin/Tools/Tool%20Config%20Syntax and seems that i can read metadata (${input.metadata.somemetadata}) but not write. Maybe <code> tag can help me but it is deprecated. Thanks for the help, Roberto