the writeJSON step currently only allows for serialization of a variable object (map, list etc) to file, but for certain operations (such as executing an adhoc curl), it would be nice if you could serialize to a string and then use that as part of the call.

For example:

sh (script: "curl -s http://localhost/rpc -d '{ \"field1\": 123 }' -H 'Content-Type: application/json'")

Could be re-written as:

def bodyMap = readJSON text: '{}'
bodyMap.field1 = 123 
def jsonStr = writeJSON json: bodyMap
sh (script: "curl -s http://localhost/rpc -d '${jsonStr}' -H 'Content-Type: application/json'")

Granted you could just serialize to file and then pass that file to the curl command.