Fix some code smells (#39)

* Fix some code smells

* Fix build

* Fix come issues

* Revert some changes

tests/mcpdotnet.Tests/McpServerBuilderExtensionsToolsTests.cs

@@ -153,10 +153,13 @@ public class McpServerBuilderExtensionsToolsTests
     {
         public EchoToolWithDi(IDependendService service)
         {
+
         }
 
         [McpTool, Description("Echoes the input back to the client.")]
+#pragma warning disable CA1822 // Mark members as static
         public Task<string> Echo(string message)
+#pragma warning restore CA1822 // Mark members as static
         {
             return Task.FromResult("hello " + message);
         }