Response headers give the following noteable things:
- allowed methods on a route
- allowed origins
- cache information
- body content length
- content type (JSON)
- date
- server info
- http status code
200 response header will look something like
Access-Control-Allow-Methods: HEAD, GET
Access-Control-Allow-Origin: *
Cache-Control: public, must-revalidate, max-age=60
Connection: close
Content-Length: 10379
Content-Type: application/json; charset=utf8
Date: Mon, 09 Mar 2015 23:01:23 GMT
Server: nginx/1.7.10
Status: 200 OK
X-Content-Type-Options: nosniff