This will create a custom alert. By default alerts will notify you by email, but you may also register a callback url. Alerts are formed as sentences:
{subject} {verb} {predicate}
An example of this construction is: {Value} {Greater Than} {100}
Which will notify you when a data point is added to the graph with a value greater then 100.

authentication is required

params:

return	This value specifies how you would like the response sent back. Possible Values: xml (Default) an xml feed json returns the feed in JSON format
subject	These are the possible values at this writing, though you should check HERE for updated values Possible Values: Value Value of the most recent datapoint in the dataset Num Data Points Total number of data points in this dataset Trend The calculated linear trend of the dataset. Note - this is calculated based on the timeframe of the graph (so if the graph shows 1 month, then this value refers to the trend for the past month)
verb	These are the possible values at this writing, though you should check HERE for updated values Possible Values: Equals Greater Than Less Than
predicate	This is the value you want to be alerted of.
callback_url	If you would like to recieve notification via a callback url instead of email. the callback will be of the form: {callback_url}?&dataset_id={dataset_id} &graph_id={graph_id} &subject={subject} &verb={verb} &predicate={predicate}