Small changes to align to the specification.

Sources/MCP/Base/Messages.swift

@@ -104,6 +104,12 @@ public struct Request<M: Method>: Hashable, Identifiable, Codable, Sendable {
                 // If params field is missing, use Empty
                 params = Empty() as! M.Parameters
             }
+        } else if M.Parameters.self == Value.self {
+            // allow missing parameter for Value parameters. This is important for AnyRequest to be able to
+            // decode a message that does have an `id` but does not have a `params` object. Otherwise the
+            // incoming message would fail to decode and would instead decode as an AnyNotification, despite
+            // the `id` parameter.
+            params = try container.decodeIfPresent(M.Parameters.self, forKey: .params) ?? (Value.null as! M.Parameters)
         } else {
             params = try container.decode(M.Parameters.self, forKey: .params)
         }

Sources/MCP/Base/Utilities/Ping.swift

@@ -1,5 +1,7 @@
 /// The Model Context Protocol includes an optional ping mechanism that allows either party to verify that their counterpart is still responsive and the connection is alive.
 /// - SeeAlso: https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/utilities/ping
 public enum Ping: Method {
+    public typealias Parameters = Empty
+    public typealias Result = Value
     public static let name: String = "ping"
 }

Sources/MCP/Server/Server.swift

@@ -401,8 +401,11 @@ public actor Server {
             return result
         }
 
-        // Ping
-        withMethodHandler(Ping.self) { _ in return Empty() }
+        // Ping. Specification shows empty dictionary as the response:
+        // https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/utilities/ping/
+        withMethodHandler(Ping.self) { params in
+            return .object([:])
+        }
     }
 
     private func setInitialState(

Sources/MCP/Server/Tools.swift

@@ -118,7 +118,11 @@ public struct Tool: Hashable, Codable, Sendable {
 public enum ListTools: Method {
     public static let name = "tools/list"
 
-    public struct Parameters: Hashable, Codable, Sendable {
+    // Specification allows optional cursor parameter:
+    // https://spec.modelcontextprotocol.io/specification/2024-11-05/server/tools/
+    public typealias Parameters = Cursor?
+
+    public struct Cursor: Hashable, Codable, Sendable {
         public let cursor: String?
 
         public init(cursor: String? = nil) {