Tooltip in Google Chart while populating chart using JSON

Question

I am populating my Google chart using JSON currently, but I need to customize tooltips as well. Currently my JSON looks like this:

{
    \"cols\": [
                


        

Answer 1

The tooltip column is badly defined; should be something like :

{"id": "", "role": "tooltip", "type": "string", "p" : { "role" : "tooltip" } }