diff --git a/xml/System/OperatingSystem.xml b/xml/System/OperatingSystem.xml
index a8bce535e97..3c86df15733 100644
--- a/xml/System/OperatingSystem.xml
+++ b/xml/System/OperatingSystem.xml
@@ -270,8 +270,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on Android.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on Android; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -302,12 +303,13 @@
         <Parameter Name="revision" Type="System.Int32" Index="3" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <param name="revision">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <param name="revision">The revision release number.</param>
+        <summary>Check for the Android version (returned by <code>uname</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given Android release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on an Android version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -334,8 +336,8 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running as WASM in a browser.</summary>
+        <returns><see langword="true" /> if the current application is running as WASM in a browser; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -362,8 +364,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on FreeBSD.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on FreeBSD; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -394,12 +397,13 @@
         <Parameter Name="revision" Type="System.Int32" Index="3" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <param name="revision">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <param name="revision">The revision release number.</param>
+        <summary>Check for the FreeBSD version (returned by <code>uname</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given FreeBSD release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on a FreeBSD version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -426,8 +430,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on iOS.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on iOS; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -457,11 +462,12 @@
         <Parameter Name="build" Type="System.Int32" Index="2" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <summary>Check for the iOS version (returned by <code>libobjc.get_operatingSystemVersion</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given iOS release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on an iOS version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -488,8 +494,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on Linux.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on Linux; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -516,8 +523,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on macOS.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on macOS; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -547,11 +555,12 @@
         <Parameter Name="build" Type="System.Int32" Index="2" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <summary>Check for the macOS version (returned by <code>libobjc.get_operatingSystemVersion</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given macOS release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on an macOS version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -580,9 +589,10 @@
         <Parameter Name="platform" Type="System.String" Index="0" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="platform">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="platform">The case-insensitive platform name. Examples: Browser, Linux, FreeBSD, Android, iOS, macOS, tvOS, watchOS, Windows.</param>
+        <summary>Indicates whether the current application is running on the specified platform.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on the specified platform; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -614,13 +624,14 @@
         <Parameter Name="revision" Type="System.Int32" Index="4" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="platform">To be added.</param>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <param name="revision">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="platform">The case-insensitive platform name. Examples: Browser, Linux, FreeBSD, Android, iOS, macOS, tvOS, watchOS, Windows.</param>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number (optional).</param>
+        <param name="build">The build release number (optional).</param>
+        <param name="revision">The revision release number (optional).</param>
+        <summary>Check for the OS with a &gt;= version comparison. This is used to guard APIs that were added in the given OS release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on the specified platform and is at least in the version specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -647,8 +658,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on tvOS.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on tvOS; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -678,11 +690,12 @@
         <Parameter Name="build" Type="System.Int32" Index="2" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <summary>Check for the tvOS version (returned by <code>libobjc.get_operatingSystemVersion</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given tvOS release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on a tvOS version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -709,8 +722,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on watchOS.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on watchOS; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -740,11 +754,12 @@
         <Parameter Name="build" Type="System.Int32" Index="2" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <summary>Check for the watchOS version (returned by <code>libobjc.get_operatingSystemVersion</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given watchOS release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on a watchOS version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -771,8 +786,9 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Indicates whether the current application is running on Windows.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on Windows; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -803,12 +819,13 @@
         <Parameter Name="revision" Type="System.Int32" Index="3" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="major">To be added.</param>
-        <param name="minor">To be added.</param>
-        <param name="build">To be added.</param>
-        <param name="revision">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="major">The major release number.</param>
+        <param name="minor">The minor release number.</param>
+        <param name="build">The build release number.</param>
+        <param name="revision">The revision release number.</param>
+        <summary>Check for the Windows version (returned by <code>RtlGetVersion</code>) with a &gt;= version comparison. This is used to guard APIs that were added in the given Windows release.</summary>
+        <returns>
+          <see langword="true" /> if the current application is running on a Windows version that is at least what was specified in the parameters; <see langword="false" /> otherwise.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>