title: VSTS REST API Caching
body: <p>I'm doing a lot of release definition requests and noticed that vsts does not provide an ETag so every request returns full json. Is this somehow configurable? </p>
  
  <p>Sample request:    </p>
  
  <blockquote>
    <p>https://{accountName}.vsrm.visualstudio.com/{project}/_apis/release/definitions/{definitionId}?api-version=4.1-preview.3</p>
  </blockquote>