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>

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