diff --git a/src/crawler/article.py b/src/crawler/article.py
index fd0c95e..a56df67 100644
--- a/src/crawler/article.py
+++ b/src/crawler/article.py
@@ -18,20 +18,36 @@ class Article:
         markdown = ""
         if including_title:
             markdown += f"# {self.title}\n\n"
-        markdown += md(self.html_content)
+        
+        if self.html_content is None or not str(self.html_content).strip():
+            markdown += "*No content available*\n"
+        else:
+            markdown += md(self.html_content)
+        
         return markdown
 
     def to_message(self) -> list[dict]:
         image_pattern = r"!\[.*?\]\((.*?)\)"
 
         content: list[dict[str, str]] = []
-        parts = re.split(image_pattern, self.to_markdown())
+        markdown = self.to_markdown()
+        
+        if not markdown or not markdown.strip():
+            return [{"type": "text", "text": "No content available"}]
+        
+        parts = re.split(image_pattern, markdown)
 
         for i, part in enumerate(parts):
             if i % 2 == 1:
                 image_url = urljoin(self.url, part.strip())
                 content.append({"type": "image_url", "image_url": {"url": image_url}})
             else:
-                content.append({"type": "text", "text": part.strip()})
+                text_part = part.strip()
+                if text_part:
+                    content.append({"type": "text", "text": text_part})
 
+        # If after processing all parts, content is still empty, provide a fallback message.
+        if not content:
+            content = [{"type": "text", "text": "No content available"}]
+        
         return content
diff --git a/src/crawler/crawler.py b/src/crawler/crawler.py
index 01a2a6e..7e5bfbd 100644
--- a/src/crawler/crawler.py
+++ b/src/crawler/crawler.py
@@ -1,11 +1,14 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
+import logging
 
 from .article import Article
 from .jina_client import JinaClient
 from .readability_extractor import ReadabilityExtractor
 
+logger = logging.getLogger(__name__)
+
 
 class Crawler:
     def crawl(self, url: str) -> Article:
@@ -19,9 +22,19 @@ class Crawler:
         #
         # Instead of using Jina's own markdown converter, we'll use
         # our own solution to get better readability results.
-        jina_client = JinaClient()
-        html = jina_client.crawl(url, return_format="html")
-        extractor = ReadabilityExtractor()
-        article = extractor.extract_article(html)
+        try:
+            jina_client = JinaClient()
+            html = jina_client.crawl(url, return_format="html")
+        except Exception as e:
+            logger.error(f"Failed to fetch URL {url} from Jina: {repr(e)}")
+            raise
+        
+        try:
+            extractor = ReadabilityExtractor()
+            article = extractor.extract_article(html)
+        except Exception as e:
+            logger.error(f"Failed to extract article from {url}: {repr(e)}")
+            raise
+        
         article.url = url
         return article
diff --git a/src/crawler/jina_client.py b/src/crawler/jina_client.py
index 8cd81ed..5cb5a08 100644
--- a/src/crawler/jina_client.py
+++ b/src/crawler/jina_client.py
@@ -23,4 +23,11 @@ class JinaClient:
             )
         data = {"url": url}
         response = requests.post("https://r.jina.ai/", headers=headers, json=data)
+        
+        if response.status_code != 200:
+            raise ValueError(f"Jina API returned status {response.status_code}: {response.text}")
+        
+        if not response.text or not response.text.strip():
+            raise ValueError("Jina API returned empty response")
+        
         return response.text
diff --git a/src/crawler/readability_extractor.py b/src/crawler/readability_extractor.py
index a3a22d0..87b3b97 100644
--- a/src/crawler/readability_extractor.py
+++ b/src/crawler/readability_extractor.py
@@ -1,15 +1,28 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
+import logging
 from readabilipy import simple_json_from_html_string
 
 from .article import Article
 
+logger = logging.getLogger(__name__)
+
 
 class ReadabilityExtractor:
     def extract_article(self, html: str) -> Article:
         article = simple_json_from_html_string(html, use_readability=True)
+        
+        content = article.get("content")
+        if not content or not str(content).strip():
+            logger.warning("Readability extraction returned empty content")
+            content = "<p>No content could be extracted from this page</p>"
+        
+        title = article.get("title")
+        if not title or not str(title).strip():
+            title = "Untitled"
+        
         return Article(
-            title=article.get("title"),
-            html_content=article.get("content"),
+            title=title,
+            html_content=content,
         )
diff --git a/tests/unit/crawler/test_article.py b/tests/unit/crawler/test_article.py
index d9bd384..0b3cddf 100644
--- a/tests/unit/crawler/test_article.py
+++ b/tests/unit/crawler/test_article.py
@@ -71,3 +71,43 @@ def test_to_message_handles_empty_html():
     result = article.to_message()
     assert isinstance(result, list)
     assert result[0]["type"] == "text"
+
+
+def test_to_markdown_handles_none_content():
+    article = Article("Test Title", None)
+    result = article.to_markdown(including_title=True)
+    assert "# Test Title" in result
+    assert "No content available" in result
+
+
+def test_to_markdown_handles_empty_string():
+    article = Article("Test Title", "")
+    result = article.to_markdown(including_title=True)
+    assert "# Test Title" in result
+    assert "No content available" in result
+
+
+def test_to_markdown_handles_whitespace_only():
+    article = Article("Test Title", "   \n  \t  ")
+    result = article.to_markdown(including_title=True)
+    assert "# Test Title" in result
+    assert "No content available" in result
+
+
+def test_to_message_handles_none_content():
+    article = Article("Title", None)
+    article.url = "http://test/"
+    result = article.to_message()
+    assert isinstance(result, list)
+    assert len(result) > 0
+    assert result[0]["type"] == "text"
+    assert "No content available" in result[0]["text"]
+
+
+def test_to_message_handles_whitespace_only_content():
+    article = Article("Title", "   \n  ")
+    article.url = "http://test/"
+    result = article.to_message()
+    assert isinstance(result, list)
+    assert result[0]["type"] == "text"
+    assert "No content available" in result[0]["text"]
diff --git a/tests/unit/crawler/test_jina_client.py b/tests/unit/crawler/test_jina_client.py
new file mode 100644
index 0000000..94edade
--- /dev/null
+++ b/tests/unit/crawler/test_jina_client.py
@@ -0,0 +1,106 @@
+# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+# SPDX-License-Identifier: MIT
+
+import pytest
+from unittest.mock import patch, Mock
+from src.crawler.jina_client import JinaClient
+
+
+class TestJinaClient:
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_success(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.text = "<html><body>Test</body></html>"
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act
+        result = client.crawl("https://example.com")
+
+        # Assert
+        assert result == "<html><body>Test</body></html>"
+        mock_post.assert_called_once()
+
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_http_error(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 500
+        mock_response.text = "Internal Server Error"
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act & Assert
+        with pytest.raises(ValueError) as exc_info:
+            client.crawl("https://example.com")
+
+        assert "status 500" in str(exc_info.value)
+
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_empty_response(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.text = ""
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act & Assert
+        with pytest.raises(ValueError) as exc_info:
+            client.crawl("https://example.com")
+
+        assert "empty response" in str(exc_info.value)
+
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_whitespace_only_response(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.text = "   \n  \t  "
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act & Assert
+        with pytest.raises(ValueError) as exc_info:
+            client.crawl("https://example.com")
+
+        assert "empty response" in str(exc_info.value)
+
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_not_found(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 404
+        mock_response.text = "Not Found"
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act & Assert
+        with pytest.raises(ValueError) as exc_info:
+            client.crawl("https://example.com")
+
+        assert "status 404" in str(exc_info.value)
+
+    @patch.dict("os.environ", {}, clear=True)
+    @patch("src.crawler.jina_client.requests.post")
+    def test_crawl_without_api_key_logs_warning(self, mock_post):
+        # Arrange
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.text = "<html>Test</html>"
+        mock_post.return_value = mock_response
+
+        client = JinaClient()
+
+        # Act
+        result = client.crawl("https://example.com")
+
+        # Assert
+        assert result == "<html>Test</html>"
diff --git a/tests/unit/crawler/test_readability_extractor.py b/tests/unit/crawler/test_readability_extractor.py
new file mode 100644
index 0000000..0e375fa
--- /dev/null
+++ b/tests/unit/crawler/test_readability_extractor.py
@@ -0,0 +1,103 @@
+# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+# SPDX-License-Identifier: MIT
+
+from unittest.mock import patch
+from src.crawler.readability_extractor import ReadabilityExtractor
+
+
+class TestReadabilityExtractor:
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_valid_content(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": "Test Article",
+            "content": "<p>Article content</p>",
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Test Article"
+        assert article.html_content == "<p>Article content</p>"
+
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_none_content(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": "Test Article",
+            "content": None,
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Test Article"
+        assert article.html_content == "<p>No content could be extracted from this page</p>"
+
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_empty_content(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": "Test Article",
+            "content": "",
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Test Article"
+        assert article.html_content == "<p>No content could be extracted from this page</p>"
+
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_whitespace_only_content(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": "Test Article",
+            "content": "   \n  \t  ",
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Test Article"
+        assert article.html_content == "<p>No content could be extracted from this page</p>"
+
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_none_title(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": None,
+            "content": "<p>Article content</p>",
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Untitled"
+        assert article.html_content == "<p>Article content</p>"
+
+    @patch("src.crawler.readability_extractor.simple_json_from_html_string")
+    def test_extract_article_with_empty_title(self, mock_simple_json):
+        # Arrange
+        mock_simple_json.return_value = {
+            "title": "",
+            "content": "<p>Article content</p>",
+        }
+        extractor = ReadabilityExtractor()
+
+        # Act
+        article = extractor.extract_article("<html>test</html>")
+
+        # Assert
+        assert article.title == "Untitled"
+        assert article.html_content == "<p>Article content</p>"
diff --git a/tests/unit/tools/test_crawl.py b/tests/unit/tools/test_crawl.py
index a21c426..15e510a 100644
--- a/tests/unit/tools/test_crawl.py
+++ b/tests/unit/tools/test_crawl.py
@@ -110,3 +110,24 @@ class TestCrawlTool:
         assert "Failed to crawl" in result
         assert "Markdown conversion error" in result
         mock_logger.error.assert_called_once()
+
+    @patch("src.tools.crawl.Crawler")
+    def test_crawl_tool_with_none_content(self, mock_crawler_class):
+        # Arrange
+        mock_crawler = Mock()
+        mock_article = Mock()
+        mock_article.to_markdown.return_value = "# Article\n\n*No content available*\n"
+        mock_crawler.crawl.return_value = mock_article
+        mock_crawler_class.return_value = mock_crawler
+
+        url = "https://example.com"
+
+        # Act
+        result = crawl_tool(url)
+
+        # Assert
+        assert isinstance(result, str)
+        result_dict = json.loads(result)
+        assert result_dict["url"] == url
+        assert "crawled_content" in result_dict
+        assert "No content available" in result_dict["crawled_content"]