How to get Microsoft Azure VM metrics

Hi All,

1.I am working on getting metrics for VMs and I am able to get them using Service Management REST API as given in belowlink:
https://convective.wordpress.com/2014/06/22/using-azure-monitoring-service-with-azure-virtual-machines/
https://convective.wordpress.com/2014/06/27/using-azure-monitoring-services-api-with-azure-cloud-services/

Is there any Azure documentation available describing this?  

2.When I tried to get Metrics for VMs using Resource Management REST API, I am getting error. I referred following links:
a.https://resources.azure.com/                                           -- Gives all the hierarchy but when I click on metrics tab for VM, it gives me metricDefinition information for that VM.
b.I am using following API call for testing with Authorization and Content-Type header:
https://management.azure.com/subscriptions/<Subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.ClassicCompute/virtualMachines/<VM_name>/metrics?api-version=2014-04-01
but getting error as below:
<Error xmlns:i="http://www.w3.org/2001/XMLSchema-instancexmlns="http://schemas.microsoft.com/windowsazure">
<Code>InvalidFilterValueParameter</Code>
<Message>Argument Null Parameter name: $filter</Message>
</Error>

                       Where can I get information regarding this “$filter” and other parameters if required for this api call?

Thanks and Regards,

Pavan Kale

<avayaelement class="contentWrapper" contenteditable="false"><avayaelement class="dcelink" contenteditable="false" id="dceLink-2" originaltext="+917709427232" style="border:1px solid rgb(106, 110, 118);color:white;box-shadow:rgba(0, 0, 0, 0.4) 0.1em 0.1em 0.7em;display:inline-block;border-radius:4px;border-collapse:separate;z-index:2000;text-decoration:none;;background-image:-webkit-gradient(linear, 0% 100%, 0% 0%, to(rgb(65, 72, 81)), color-stop(0.5, rgb(27, 36, 45)));">+917709427232</avayaelement></avayaelement>