Clear tool cache at start of ListToolsAsync to prevent unbounded growth

Author: Tarek Mahmoud Sayed

src/ModelContextProtocol.Core/Client/McpClient.Methods.cs

@@ -176,6 +176,8 @@ public async ValueTask<IList<McpClientTool>> ListToolsAsync(
         RequestOptions? options = null,
         CancellationToken cancellationToken = default)
     {
+        ToolCacheClearing?.Invoke();
+
         List<McpClientTool>? tools = null;
         ListToolsRequestParams requestParams = new() { Meta = options?.GetMetaForRequest() };
         do
@@ -213,6 +215,11 @@ public async ValueTask<IList<McpClientTool>> ListToolsAsync(
     /// </summary>
     internal Action<Tool, string>? ToolRejected;
 
+    /// <summary>
+    /// Invoked before enumerating tools to clear any previously cached tool definitions.
+    /// </summary>
+    internal Action? ToolCacheClearing;
+
     /// <summary>
     /// Retrieves a list of available tools from the server.
     /// </summary>

src/ModelContextProtocol.Core/Client/McpClientImpl.cs

@@ -72,6 +72,7 @@ internal McpClientImpl(ITransport transport, string endpointName, McpClientOptio
 
         ToolDiscovered = tool => _toolCache[tool.Name] = tool;
         ToolRejected = (tool, reason) => LogToolRejected(tool.Name, reason);
+        ToolCacheClearing = () => _toolCache.Clear();
     }
 
     private void RegisterHandlers(McpClientOptions options, NotificationHandlers notificationHandlers, RequestHandlers requestHandlers)