diff --git a/scripts/extractor.js b/scripts/extractor.js
index e4007a7..7d2b15f 100644
--- a/scripts/extractor.js
+++ b/scripts/extractor.js
@@ -11,8 +11,11 @@ class Extractor {
      * @param {...any} args itemsSelector, fieldSelectors, and more args to specify target urls.
      */
     task(...args) {
-        if (!testArgs(...args))
-            throw new Error(`Invalid call arguments.\n\n${signitures}\n\n`);
+        if (!testArgs(...args)) {
+            console.log(`Invalid call arguments.\n\n${argsToString(...args)}\n${signitures}\n`);
+            // break call chain to avoid unexpected task running
+            return undefined;
+        }
         // given >2 arguments means the task specifies target page, 
         // so it won't accept last task result as url list.
         // in this case, former tasks are useless, can be cleared.
diff --git a/scripts/tools.js b/scripts/tools.js
index 7e076a0..c779b5c 100644
--- a/scripts/tools.js
+++ b/scripts/tools.js
@@ -1,7 +1,4 @@
 const signitures = `
-# DataExtracter Help
-----------------------------
-
 ## Usage
 new Extractor().task(...args).task(...args).start();
 
@@ -14,7 +11,7 @@ task(itemsSelector:string, fieldSelectors:string, url:string, pages:number[])
 task(itemsSelector:string, fieldSelectors:string[], urls:string[])
 task(itemsSelector:string, fieldSelectors:string[], urls:ExtractResult)
 
-See detail help in:
+## See Detailed Help:
 https://git.jebbs.co/jebbs/data-extracter-extesion
 `.trim();
 
@@ -95,4 +92,8 @@ function testArgs(...args) {
     function testArrayVals(arr, tester) {
         return arr.reduce((p, c) => p && tester(c), true);
     }
+}
+
+function argsToString(...args) {
+    return args.map(v => (v instanceof Array ? `[${v.join(', ')}]` : v.toString())).join(', ');
 }
\ No newline at end of file