How to deal with datafield returned from webservice request

[peterhuppertz]

I invoke a Webservice Function and I see the correct data returned. However, I don't know how to use it in subsequent steps of the workflow.
The data returned looks like this:

'{
    "error": false,
    "data": {
        "cm": {
            "id": 563,
            "course": 16,
            "module": 1
        },
        "warnings": []
    }
}'

However when I try to use {data->cm->id} it does not get replace in an email. What is the correct way to reference the returned object?