What payload to get the latest version of a Pass?

I have my own pass kit server. After adding a pass, the device asks first for other passes, and then tries to update them via

Code Block
webServiceURL/version/passes/passTypeIdentifier/serialNumber

From the documentation, it should

return HTTP status 200 with a payload of the pass data.

What it doesn't say - should it be the whole pkpass package? Or is it possible to update just some key/value pairs?
What payload to get the latest version of a Pass?
 
 
Q