This extension “Chamindac.vsts.release.task.download-artifacts” for VSTS and TFS 2015.2.1 upwards, can be used to filter for build artifacts by name, and download only required artifact(s), to the release agent machine. The requirement for this extension is explained in post “Multiple Build Artifacts–TFS 2015/VSTS Builds”. Source code for this extension is available in Github.
Extension “Chamindac.vsts.release.task.download-artifacts” can be downloaded/installed from VSTS Marketplace. To install to VS Team Services click on install, or download for on-premise TFS 2015 (TFS 2015.2.1 upwards supported).