🔧 fix: API Key Handling for GoogleSearch and TavilySearch Tools (#3541)

* fix: get user-provided API key using environment variable names as keys

* feat: Add error handling for missing API key and search engine ID

* feat: Add GoogleSearch and TavilySearchResults specs for environment variables handling

---------

Co-authored-by: Dongwoo Jeong <dongwoo.jeong@lge.com>

api/app/clients/tools/structured/specs/TavilySearchResults.spec.js

@@ -0,0 +1,38 @@
+const TavilySearchResults = require('../TavilySearchResults');
+
+jest.mock('node-fetch');
+jest.mock('@langchain/core/utils/env');
+
+describe('TavilySearchResults', () => {
+  let originalEnv;
+  const mockApiKey = 'mock_api_key';
+
+  beforeAll(() => {
+    originalEnv = { ...process.env };
+  });
+
+  beforeEach(() => {
+    jest.resetModules();
+    process.env = {
+      ...originalEnv,
+      TAVILY_API_KEY: mockApiKey,
+    };
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+    process.env = originalEnv;
+  });
+
+  it('should throw an error if TAVILY_API_KEY is missing', () => {
+    delete process.env.TAVILY_API_KEY;
+    expect(() => new TavilySearchResults()).toThrow('Missing TAVILY_API_KEY environment variable.');
+  });
+
+  it('should use mockApiKey when TAVILY_API_KEY is not set in the environment', () => {
+    const instance = new TavilySearchResults({
+      TAVILY_API_KEY: mockApiKey,
+    });
+    expect(instance.apiKey).toBe(mockApiKey);
+  });
+});