Add docstrings to preconditions.

src/Discord.Net.Commands/Attributes/Preconditions/RequireBotPermissionAttribute.cs

@@ -5,17 +5,38 @@ using System.Threading.Tasks;
 
 namespace Discord.Commands
 {
+    /// <summary>
+    /// This attribute requires that the bot has a speicifed permission in the channel a command is invoked in.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
     public class RequireBotPermissionAttribute : PreconditionAttribute
     {
         public GuildPermission? GuildPermission { get; }
         public ChannelPermission? ChannelPermission { get; }
 
+        /// <summary>
+        /// Require that the bot account has a specified GuildPermission
+        /// </summary>
+        /// <remarks>This precondition will always fail if the command is being invoked in a private channel.</remarks>
+        /// <param name="permission">The GuildPermission that the bot must have. Multiple permissions can be specified by ORing or ANDing the permissions together.</param>
         public RequireBotPermissionAttribute(GuildPermission permission)
         {
             GuildPermission = permission;
             ChannelPermission = null;
         }
+        /// <summary>
+        /// Require that the bot account has a specified ChannelPermission.
+        /// </summary>
+        /// <param name="permission">The ChannelPermission that the bot must have. Multiple permissions can be specified by ORing or ANDing the permissions together.</param>
+        /// <example>
+        /// <code language="c#">
+        ///     [Command("permission")]
+        ///     [RequireBotPermission(ChannelPermission.ManageMessages)]
+        ///     public async Task Purge()
+        ///     {
+        ///     }
+        /// </code>
+        /// </example>
         public RequireBotPermissionAttribute(ChannelPermission permission)
         {
             ChannelPermission = permission;

src/Discord.Net.Commands/Attributes/Preconditions/RequireContextAttribute.cs

@@ -11,11 +11,27 @@ namespace Discord.Commands
         Group = 0x04
     }
 
+    /// <summary>
+    /// Require that the command be invoked in a specified context.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
     public class RequireContextAttribute : PreconditionAttribute
     {
         public ContextType Contexts { get; }
 
+        /// <summary>
+        /// Require that the command be invoked in a specified context.
+        /// </summary>
+        /// <param name="contexts">The type of context the command can be invoked in. Multiple contexts can be speicifed by ORing the contexts together.</param>
+        /// <example>
+        /// <code language="c#">
+        ///     [Command("private_only")]
+        ///     [RequireContext(ContextType.DM | ContextType.Group)]
+        ///     public async Task PrivateOnly()
+        ///     {
+        ///     }
+        /// </code>
+        /// </example>
         public RequireContextAttribute(ContextType contexts)
         {
             Contexts = contexts;

src/Discord.Net.Commands/Attributes/Preconditions/RequireOwnerAttribute.cs

@@ -6,6 +6,10 @@ using Discord;
 
 namespace Discord.Commands
 {
+    /// <summary>
+    /// Require that the command is invoked by the owner of the bot.
+    /// </summary>
+    /// <remarks>This precondition will only work if the bot is a bot account.</remarks>
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
     public class RequireOwnerAttribute : PreconditionAttribute
     {

src/Discord.Net.Commands/Attributes/Preconditions/RequireUserPermissionAttribute.cs

@@ -3,17 +3,39 @@ using System.Threading.Tasks;
 
 namespace Discord.Commands
 {
+    /// <summary>
+    /// This attribute requires that the user invoking the command has a specified permission.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
     public class RequireUserPermissionAttribute : PreconditionAttribute
     {
         public GuildPermission? GuildPermission { get; }
         public ChannelPermission? ChannelPermission { get; }
 
+        /// <summary>
+        /// Require that the user invoking the command has a specified GuildPermission
+        /// </summary>
+        /// <remarks>This precondition will always fail if the command is being invoked in a private channel.</remarks>
+        /// <param name="permission">The GuildPermission that the user must have. Multiple permissions can be specified by ORing or ANDing the permissions together.</param>
         public RequireUserPermissionAttribute(GuildPermission permission)
         {
             GuildPermission = permission;
             ChannelPermission = null;
         }
+        /// <summary>
+        /// Require that the user invoking the command has a specified ChannelPermission.
+        /// </summary>
+        /// <param name="permission">The ChannelPermission that the user must have. Multiple permissions can be specified by ORing or ANDing the permissions together.</param>
+        /// <example>
+        /// <code language="c#">
+        ///     [Command("permission")]
+        ///     [RequireUserPermission(ChannelPermission.ReadMessageHistory & ChannelPermission.ReadMessages)]
+        ///     public async Task HasPermission()
+        ///     {
+        ///         await ReplyAsync("You can read messages and the message history!");
+        ///     }
+        /// </code>
+        /// </example>
         public RequireUserPermissionAttribute(ChannelPermission permission)
         {
             ChannelPermission = permission;