diff --git a/.changeset/fix-register-tool-task-args.md b/.changeset/fix-register-tool-task-args.md
new file mode 100644
index 000000000..40d05e654
--- /dev/null
+++ b/.changeset/fix-register-tool-task-args.md
@@ -0,0 +1,5 @@
+---
+'@modelcontextprotocol/server': patch
+---
+
+Fix `registerToolTask` to pass empty args object to `createTask` handler when no `inputSchema` is provided, allowing two-argument `(args, ctx)` handler signatures to work correctly.
diff --git a/packages/server/src/server/mcp.ts b/packages/server/src/server/mcp.ts
index e35871096..1d1533008 100644
--- a/packages/server/src/server/mcp.ts
+++ b/packages/server/src/server/mcp.ts
@@ -1042,10 +1042,10 @@ function createToolExecutor(inputSchema: AnySchema | undefined, handler: AnyTool
                 throw new Error('No task store provided.');
             }
             const taskCtx: CreateTaskServerContext = { ...ctx, task: { store: ctx.task.store, requestedTtl: ctx.task?.requestedTtl } };
-            if (inputSchema) {
-                return taskHandler.createTask(args, taskCtx);
+            if (inputSchema || taskHandler.createTask.length > 1) {
+                return taskHandler.createTask(inputSchema ? args : {}, taskCtx);
             }
-            // When no inputSchema, call with just ctx (the handler expects (ctx) signature)
+            // When no inputSchema and handler expects single arg, call with just ctx
             return (taskHandler.createTask as (ctx: CreateTaskServerContext) => CreateTaskResult | Promise<CreateTaskResult>)(taskCtx);
         };
     }