Fix seealso for preconditions and add missing descriptions

docs/_overwrites/Commands/PreconditionAttribute.Overwrites.md

@@ -1,7 +1,5 @@
 ---
 uid: Discord.Commands.PreconditionAttribute
-seealso:
-    - linkId: Discord.Commands.ParameterPreconditionAttribute
 remarks: *content
 ---
 
@@ -12,8 +10,6 @@ method-level for a command.
 
 ---
 uid: Discord.Commands.ParameterPreconditionAttribute
-seealso:
-    - linkId: Discord.Commands.PreconditionAttribute
 remarks: *content
 ---
 

src/Discord.Net.Commands/Attributes/ParameterPreconditionAttribute.cs

@@ -6,6 +6,7 @@ namespace Discord.Commands
     /// <summary>
     ///     Requires the parameter to pass the specified precondition before execution can begin.
     /// </summary>
+    /// <seealso cref="PreconditionAttribute"/>
     [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = true, Inherited = true)]
     public abstract class ParameterPreconditionAttribute : Attribute
     {

src/Discord.Net.Commands/Attributes/PreconditionAttribute.cs

@@ -3,12 +3,15 @@ using System.Threading.Tasks;
 
 namespace Discord.Commands
 {
-    /// <summary> Requires the module or class to pass the specified precondition before execution can begin. </summary>
+    /// <summary>
+    ///     Requires the module or class to pass the specified precondition before execution can begin.
+    /// </summary>
+    /// <seealso cref="ParameterPreconditionAttribute"/>
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
     public abstract class PreconditionAttribute : Attribute
     {
         /// <summary>
-        ///     Specify a group that this precondition belongs to.
+        ///     Specifies a group that this precondition belongs to.
         /// </summary>
         /// <remarks>
         ///     <see cref="Preconditions" /> of the same group require only one of the preconditions to pass in order to
@@ -17,6 +20,12 @@ namespace Discord.Commands
         /// </remarks>
         public string Group { get; set; } = null;
 
+        /// <summary>
+        ///     Checks if the <paramref name="command"/> has the sufficient permission to be executed.
+        /// </summary>
+        /// <param name="context">The context of the command.</param>
+        /// <param name="command">The command being executed.</param>
+        /// <param name="services">The service collection used for dependency injection.</param>
         public abstract Task<PreconditionResult> CheckPermissionsAsync(ICommandContext context, CommandInfo command, IServiceProvider services);
     }
 }