How do I set the post request body of a web service on the design surface

I created a source against my local couchdb install (http://localhost:5984)
I then created a web service as seen in the image below


I then saved it and placed it on the design surface passing :

{"docs": [ {"_id": "my_doc", "number": 23}, {"_id": "_design/app", "updates": { "accumulate": "function (doc, req) { var inc_amount = parseInt(req.query.amount); doc.number = doc.number + inc_amount; return [doc, \"I incremented \" + doc._id + \" by \" + inc_amount]; }" } } ]}

into the postBody variable and executed it. I got an error message as seen in the image below.


How can I pass JSON data into the request and have it execute?