Wow, I was calling the wrong endpoint.

lib/cloudability/client/usage_reports.rb

@@ -7,7 +7,7 @@ module UsageReports
       # @see http://developers.cloudability.com/resources/usage/
       # @return [Array] array of Hashie::Mashes
       def usage_reports
-        request = get '/1/reporting/usage'
+        request = get '/1/reporting'
         convert_to_mashes request
       end
 

spec/cloduability/usage_spec.rb

@@ -8,12 +8,12 @@
 
   describe '#usage_reports' do
     it 'should be an array' do
-      stub_get('/1/reporting/usage?auth_token=token', 'usage/reports')
+      stub_get('/1/reporting?auth_token=token', 'usage/reports')
       @client.usage_reports.should be_kind_of Array
     end
 
     it 'should be an array of Hashie::Mashes' do
-      stub_get('/1/reporting/usage?auth_token=token', 'usage/reports')
+      stub_get('/1/reporting?auth_token=token', 'usage/reports')
       @client.usage_reports.each{|report| report.should be_kind_of Hashie::Mash }
     end
   end

spec/fixtures/usage/reports

@@ -0,0 +1,18 @@
+HTTP/1.1 200 OK
+Server: nginx/1.4.4
+Date: Fri, 27 Dec 2013 05:31:15 GMT
+Content-Type: application/json
+Content-Length: 44476
+Connection: keep-alive
+Status: 200 OK
+Strict-Transport-Security: max-age=31536000
+Set-Cookie: _mkra_ctxt=1f0f9e994c1eda7c8aaca1c638e169e7--200; path=/; secure
+X-UA-Compatible: IE=Edge,chrome=1
+ETag: "575c428e918fe64a860eaf6e6cc8ba2e"
+Cache-Control: max-age=0, private, must-revalidate
+X-Request-Id: 9534fd1ae2484ed36a74011e9f5816e4
+X-Runtime: 1.713328
+X-Rack-Cache: miss
+Origin: app.cloudability.com
+
+[{"id":2,"category":"Utilization","title":"Longest Running","description":null,"end_date":"today","start_date":"last week","end_date_is_relative":true,"start_date_is_relative":true,"owned_by_user":false,"shared":false,"custom":false,"metrics":[{"type":"metric","name":"hours_since_launch","label":"Hours Since Launch","description":"Hours since instance launch","data_type":"float","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"time","name":"Time"}},{"type":"metric","name":"utilization_hours","label":"Utilization Hours","description":"Utilization hours","data_type":"integer","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"usage","name":"Usage"}},{"type":"metric","name":"avg_estimated_hourly_cost","label":"Avg Estimated Hourly Instance Cost","description":"Average estimated hourly cost","data_type":"currency","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"billing","name":"Billing"}}],"dimensions":[{"type":"dimension","name":"instance_identifier","label":"Instance ID","description":"Instance ID","data_type":"string","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"common","name":"Common"}},{"type":"dimension","name":"instance_size","label":"Size","description":"Size of the Instance","data_type":"string","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"common","name":"Common"}}],"filters":[],"report_dimension_links":[]},{"id":3,"category":"Utilization","title":"Instance Aging","description":null,"end_date":"today","start_date":"last week","end_date_is_relative":true,"start_date_is_relative":true,"owned_by_user":false,"shared":false,"custom":false,"metrics":[{"type":"metric","name":"terminated_instances","label":"Terminated Instances","description":"Number of terminated instances","data_type":"integer","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"usage","name":"Usage"}},{"type":"metric","name":"running_instances","label":"Running Instances","description":"Number of running instances","data_type":"integer","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"usage","name":"Usage"}}],"dimensions":[{"type":"dimension","name":"days_since_launch","label":"Days Alive","description":"Days since instance was launched","data_type":"integer","group":{"key":"compute","name":"Compute"},"sub_group":{"key":"usage","name":"Usage"}}],"filters":[],"report_dimension_links":[]}]