how to get error details for usergrid functions in Node.js

I am using node.js sdk for operations on a Baas collection. When I try to create an entity with the same name I get a 500 error. I figured out through Curl that the entity wasn't created because it was a duplicate, the name field was not unique. The code I am using is below. I only get to know if its success or error. Is there a way to get the error details?

client.createEntity(opts, function(err, o) {
if (err) {
res.jsonp(500, "Could not create entity.");//Need error details here return;
}
o.set(w);
o.save(function(err) {
if (err) {
res.jsonp(500, err);
return;
}
res.send(201);
});
});