Example of simple webpi feed used to extract a zip or install a msi

webpi-feed.xml

<?xml version="1.0"?>
<feed xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.w3.org/2005/Atom">
  <title>Web Platform Installer 4.0 Feed</title>
  <updated>2013-12-05T16:00:10Z</updated>
  <id>http://url/to/Feed.xml</id>
  <link href="http://url/to/Feed.xml" />
  <author>
    <name>Author Name</name>
    <uri>http://url</uri>
  </author>
  <entry>
    <productId>CustomTool</productId>
    <title>CustomTool</title>
    <searchExclude />
    <version>1.0.0</version>
    <updated>2016-10-06T11:00:00Z</updated>
    <published>2016-10-06T11:00:00Z</published>
    <id>CustomTool</id>
    <summary resourceName="CustomTool">CustomTool</summary>
    <longSummary resourceName="CustomTool">CustomTool</longSummary>
    <link href="http://umbraco.com" />
    <author>
      <name>Author Name</name>
      <uri>http://zip author url</uri>
    </author>
    <installers>
      <installer>
        <id>1</id>
        <helpLink />
        <installerFile>
          <fileSize>86605</fileSize>
          <installerURL>http://url/to/custom.zip</installerURL>
          <sha1>8B89C4B165362B323756BFCDA662940F93F33442</sha1>
        </installerFile>
		<installCommands>
          <unzip>
            <zipFile>%InstallerFile%</zipFile>
            <targetDirectory>%ProgramFiles%\folder</targetDirectory>
          </unzip>
		  <cmdline>
            <exe>%ProgramFiles%\folder\run.exe</exe>
            <commandLineArguments>argument goes here</commandLineArguments>
          </cmdline>
        </installCommands>
      </installer>
    </installers>
  </entry>
  <entry>
    <productId>ApplicationRequestRouting</productId>
    <title>Application Request Routing v3</title>
    <searchExclude />
    <version>3.0.1952</version>
    <updated>2017-07-18T10:00:00Z</updated>
    <published>2017-07-18T10:00:00Z</published>
    <id>ApplicationRequestRouting</id>
    <summary resourceName="ApplicationRequestRouting">ApplicationRequestRouting</summary>
    <longSummary resourceName="ApplicationRequestRouting">ApplicationRequestRouting</longSummary>
    <link href="https://www.iis.net/downloads/microsoft/application-request-routing" />
    <author>
      <name>Microsoft</name>
      <uri>https://www.iis.net/downloads/microsoft/application-request-routing</uri>
    </author>
    <installers>
      <installer>
        <id>1</id>
        <helpLink />
        <installerFile>
          <fileSize>2076672</fileSize>
          <installerURL>http://download-url/requestRouter_amd64.msi</installerURL>
          <sha1>5F4F24058DCD675DA46DC0C4B17969D41FCE68C1</sha1>
        </installerFile>
		<installCommands>
          <msiInstall>
            <msi>%InstallerFile%</msi>
          </msiInstall>
        </installCommands>
      </installer>
    </installers>
  </entry>
</feed>

fileSize, sha1 and possibly installerURL need to be updated each time a build is updated. So if VSTS is used to build the custom.zip in the example above the url to the artifact needs to be public and then the fileSize and sha1 needs to match that of the file (custom.zip).

Here is a reference to the xml schema and the various elements of the feed: https://technet.microsoft.com/en-us/library/ee424350(v=ws.10).aspx