What is the best way to 'see' the data returned by the ajax calls the grid makes for debugging purposes?

I have a grid thats not displaying data, I suspect something is up with the json data stream, but don't know what to look at.

I realize I can just call the same file specified in the url setting of the grid, but it's setup to take parameters and what I'd really like is a way to see the response while it's running, either through a debugger or by throwing an alert(Variablename); into my code somewhere.

Has anyone else come across this need? is there an easy way to see this?