Update prompt and grep tool definition to limit context size (#18780)

packages/core/src/tools/grep.test.ts

@@ -498,6 +498,41 @@ describe('GrepTool', () => {
       expect(result.llmContent).toContain('File: sub/fileC.txt');
       expect(result.llmContent).toContain('L1: another world in sub dir');
     });
+
+    it('should return only file paths when names_only is true', async () => {
+      const params: GrepToolParams = {
+        pattern: 'world',
+        names_only: true,
+      };
+      const invocation = grepTool.build(params);
+      const result = await invocation.execute(abortSignal);
+
+      expect(result.llmContent).toContain('Found 2 files with matches');
+      expect(result.llmContent).toContain('fileA.txt');
+      expect(result.llmContent).toContain('sub/fileC.txt');
+      expect(result.llmContent).not.toContain('L1:');
+      expect(result.llmContent).not.toContain('hello world');
+    });
+
+    it('should filter out matches based on exclude_pattern', async () => {
+      await fs.writeFile(
+        path.join(tempRootDir, 'copyright.txt'),
+        'Copyright 2025 Google LLC\nCopyright 2026 Google LLC',
+      );
+
+      const params: GrepToolParams = {
+        pattern: 'Copyright .* Google LLC',
+        exclude_pattern: '2026',
+        dir_path: '.',
+      };
+      const invocation = grepTool.build(params);
+      const result = await invocation.execute(abortSignal);
+
+      expect(result.llmContent).toContain('Found 1 match');
+      expect(result.llmContent).toContain('copyright.txt');
+      expect(result.llmContent).toContain('Copyright 2025 Google LLC');
+      expect(result.llmContent).not.toContain('Copyright 2026 Google LLC');
+    });
   });
 
   describe('getDescription', () => {