Align InitializeResult.instructions XML docs with latest MCP spec guidance (#1290)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>
Co-authored-by: Stephen Halter <halter73@gmail.com>

Author: 3 people

src/ModelContextProtocol.Core/Client/McpClient.cs

@@ -35,11 +35,11 @@ public abstract partial class McpClient : McpSession
     /// <remarks>
     /// <para>
     /// This property contains instructions provided by the server during initialization that explain
-    /// how to effectively use its capabilities. These instructions can include details about available
-    /// tools, expected input formats, limitations, or any other helpful information.
+    /// how to effectively use its capabilities. They should focus on guidance that helps a model
+    /// use the server effectively and should avoid duplicating tool, prompt, or resource descriptions.
     /// </para>
     /// <para>
-    /// This can be used by clients to improve an LLM's understanding of available tools, prompts, and resources.
+    /// This can be used by clients to improve an LLM's understanding of how to use the server.
     /// It can be thought of like a "hint" to the model and can be added to a system prompt.
     /// </para>
     /// </remarks>

src/ModelContextProtocol.Core/Protocol/InitializeResult.cs

@@ -65,9 +65,10 @@ public sealed class InitializeResult : Result
     /// </summary>
     /// <remarks>
     /// <para>
-    /// These instructions provide guidance to clients on how to effectively use the server's capabilities.
-    /// They can include details about available tools, expected input formats, limitations,
-    /// or any other information that helps clients interact with the server properly.
+    /// These instructions should focus on guidance that helps a model use the server effectively,
+    /// such as workflow tips, capability relationships, and server-specific conventions.
+    /// They should avoid repeating tool descriptions, prompt descriptions, or resource descriptions
+    /// that are already available through other protocol responses.
     /// </para>
     /// <para>
     /// Client applications often use these instructions as system messages for LLM interactions

src/ModelContextProtocol.Core/Server/McpServerOptions.cs

@@ -54,8 +54,9 @@ public sealed class McpServerOptions
     /// </summary>
     /// <remarks>
     /// These instructions are sent to clients during the initialization handshake and provide
-    /// guidance on how to effectively use the server's capabilities. They can include details
-    /// about available tools, expected input formats, limitations, or other helpful information.
+    /// guidance on how to effectively use the server's capabilities. They should focus on
+    /// information that helps models use the server effectively and should not duplicate
+    /// tool, prompt, or resource descriptions already exposed elsewhere.
     /// Client applications typically use these instructions as system messages for LLM interactions
     /// to provide context about available functionality.
     /// </remarks>