diff --git a/api/services/tools/tools_transform_service.py b/api/services/tools/tools_transform_service.py
index 845e14ca70..6b36ed0eb7 100644
--- a/api/services/tools/tools_transform_service.py
+++ b/api/services/tools/tools_transform_service.py
@@ -262,7 +262,7 @@ class ToolTransformService:
                 author=user.name if user else "Anonymous",
                 name=tool.name,
                 label=I18nObject(en_US=tool.name, zh_Hans=tool.name),
-                description=I18nObject(en_US=tool.description, zh_Hans=tool.description),
+                description=I18nObject(en_US=tool.description or "", zh_Hans=tool.description or ""),
                 parameters=ToolTransformService.convert_mcp_schema_to_parameter(tool.inputSchema),
                 labels=[],
             )
diff --git a/api/tests/unit_tests/services/tools/test_mcp_tools_transform.py b/api/tests/unit_tests/services/tools/test_mcp_tools_transform.py
new file mode 100644
index 0000000000..fb0139932b
--- /dev/null
+++ b/api/tests/unit_tests/services/tools/test_mcp_tools_transform.py
@@ -0,0 +1,212 @@
+"""Test cases for MCP tool transformation functionality."""
+
+from unittest.mock import Mock
+
+import pytest
+
+from core.mcp.types import Tool as MCPTool
+from core.tools.entities.api_entities import ToolApiEntity, ToolProviderApiEntity
+from core.tools.entities.common_entities import I18nObject
+from core.tools.entities.tool_entities import ToolProviderType
+from models.tools import MCPToolProvider
+from services.tools.tools_transform_service import ToolTransformService
+
+
+@pytest.fixture
+def mock_user():
+    """Provides a mock user object."""
+    user = Mock()
+    user.name = "Test User"
+    return user
+
+
+@pytest.fixture
+def mock_provider(mock_user):
+    """Provides a mock MCPToolProvider with a loaded user."""
+    provider = Mock(spec=MCPToolProvider)
+    provider.load_user.return_value = mock_user
+    return provider
+
+
+@pytest.fixture
+def mock_provider_no_user():
+    """Provides a mock MCPToolProvider with no user."""
+    provider = Mock(spec=MCPToolProvider)
+    provider.load_user.return_value = None
+    return provider
+
+
+@pytest.fixture
+def mock_provider_full(mock_user):
+    """Provides a fully configured mock MCPToolProvider for detailed tests."""
+    provider = Mock(spec=MCPToolProvider)
+    provider.id = "provider-id-123"
+    provider.server_identifier = "server-identifier-456"
+    provider.name = "Test MCP Provider"
+    provider.provider_icon = "icon.png"
+    provider.authed = True
+    provider.masked_server_url = "https://*****.com/mcp"
+    provider.timeout = 30
+    provider.sse_read_timeout = 300
+    provider.masked_headers = {"Authorization": "Bearer *****"}
+    provider.decrypted_headers = {"Authorization": "Bearer secret-token"}
+
+    # Mock timestamp
+    mock_updated_at = Mock()
+    mock_updated_at.timestamp.return_value = 1234567890
+    provider.updated_at = mock_updated_at
+
+    provider.load_user.return_value = mock_user
+    return provider
+
+
+@pytest.fixture
+def sample_mcp_tools():
+    """Provides sample MCP tools for testing."""
+    return {
+        "simple": MCPTool(
+            name="simple_tool", description="A simple test tool", inputSchema={"type": "object", "properties": {}}
+        ),
+        "none_desc": MCPTool(name="tool_none_desc", description=None, inputSchema={"type": "object", "properties": {}}),
+        "complex": MCPTool(
+            name="complex_tool",
+            description="A tool with complex parameters",
+            inputSchema={
+                "type": "object",
+                "properties": {
+                    "text": {"type": "string", "description": "Input text"},
+                    "count": {"type": "integer", "description": "Number of items", "minimum": 1, "maximum": 100},
+                    "options": {"type": "array", "items": {"type": "string"}, "description": "List of options"},
+                },
+                "required": ["text"],
+            },
+        ),
+    }
+
+
+class TestMCPToolTransform:
+    """Test cases for MCP tool transformation methods."""
+
+    def test_mcp_tool_to_user_tool_with_none_description(self, mock_provider):
+        """Test that mcp_tool_to_user_tool handles None description correctly."""
+        # Create MCP tools with None description
+        tools = [
+            MCPTool(
+                name="tool1",
+                description=None,  # This is the case that caused the error
+                inputSchema={"type": "object", "properties": {}},
+            ),
+            MCPTool(
+                name="tool2",
+                description=None,
+                inputSchema={
+                    "type": "object",
+                    "properties": {"param1": {"type": "string", "description": "A parameter"}},
+                },
+            ),
+        ]
+
+        # Call the method
+        result = ToolTransformService.mcp_tool_to_user_tool(mock_provider, tools)
+
+        # Verify the result
+        assert len(result) == 2
+        assert all(isinstance(tool, ToolApiEntity) for tool in result)
+
+        # Check first tool
+        assert result[0].name == "tool1"
+        assert result[0].author == "Test User"
+        assert isinstance(result[0].label, I18nObject)
+        assert result[0].label.en_US == "tool1"
+        assert isinstance(result[0].description, I18nObject)
+        assert result[0].description.en_US == ""  # Should be empty string, not None
+        assert result[0].description.zh_Hans == ""
+
+        # Check second tool
+        assert result[1].name == "tool2"
+        assert result[1].description.en_US == ""
+        assert result[1].description.zh_Hans == ""
+
+    def test_mcp_tool_to_user_tool_with_description(self, mock_provider):
+        """Test that mcp_tool_to_user_tool handles normal description correctly."""
+        # Create MCP tools with description
+        tools = [
+            MCPTool(
+                name="tool_with_desc",
+                description="This is a test tool that does something useful",
+                inputSchema={"type": "object", "properties": {}},
+            )
+        ]
+
+        # Call the method
+        result = ToolTransformService.mcp_tool_to_user_tool(mock_provider, tools)
+
+        # Verify the result
+        assert len(result) == 1
+        assert isinstance(result[0], ToolApiEntity)
+        assert result[0].name == "tool_with_desc"
+        assert result[0].description.en_US == "This is a test tool that does something useful"
+        assert result[0].description.zh_Hans == "This is a test tool that does something useful"
+
+    def test_mcp_tool_to_user_tool_with_no_user(self, mock_provider_no_user):
+        """Test that mcp_tool_to_user_tool handles None user correctly."""
+        # Create MCP tool
+        tools = [MCPTool(name="tool1", description="Test tool", inputSchema={"type": "object", "properties": {}})]
+
+        # Call the method
+        result = ToolTransformService.mcp_tool_to_user_tool(mock_provider_no_user, tools)
+
+        # Verify the result
+        assert len(result) == 1
+        assert result[0].author == "Anonymous"
+
+    def test_mcp_tool_to_user_tool_with_complex_schema(self, mock_provider, sample_mcp_tools):
+        """Test that mcp_tool_to_user_tool correctly converts complex input schemas."""
+        # Use complex tool from fixtures
+        tools = [sample_mcp_tools["complex"]]
+
+        # Call the method
+        result = ToolTransformService.mcp_tool_to_user_tool(mock_provider, tools)
+
+        # Verify the result
+        assert len(result) == 1
+        assert result[0].name == "complex_tool"
+        assert result[0].parameters is not None
+        # The actual parameter conversion is handled by convert_mcp_schema_to_parameter
+        # which should be tested separately
+
+    def test_mcp_provider_to_user_provider_for_list(self, mock_provider_full):
+        """Test mcp_provider_to_user_provider with for_list=True."""
+        # Set tools data with null description
+        mock_provider_full.tools = '[{"name": "tool1", "description": null, "inputSchema": {}}]'
+
+        # Call the method with for_list=True
+        result = ToolTransformService.mcp_provider_to_user_provider(mock_provider_full, for_list=True)
+
+        # Verify the result
+        assert isinstance(result, ToolProviderApiEntity)
+        assert result.id == "provider-id-123"  # Should use provider.id when for_list=True
+        assert result.name == "Test MCP Provider"
+        assert result.type == ToolProviderType.MCP
+        assert result.is_team_authorization is True
+        assert result.server_url == "https://*****.com/mcp"
+        assert len(result.tools) == 1
+        assert result.tools[0].description.en_US == ""  # Should handle None description
+
+    def test_mcp_provider_to_user_provider_not_for_list(self, mock_provider_full):
+        """Test mcp_provider_to_user_provider with for_list=False."""
+        # Set tools data with description
+        mock_provider_full.tools = '[{"name": "tool1", "description": "Tool description", "inputSchema": {}}]'
+
+        # Call the method with for_list=False
+        result = ToolTransformService.mcp_provider_to_user_provider(mock_provider_full, for_list=False)
+
+        # Verify the result
+        assert isinstance(result, ToolProviderApiEntity)
+        assert result.id == "server-identifier-456"  # Should use server_identifier when for_list=False
+        assert result.server_identifier == "server-identifier-456"
+        assert result.timeout == 30
+        assert result.sse_read_timeout == 300
+        assert result.original_headers == {"Authorization": "Bearer secret-token"}
+        assert len(result.tools) == 1
+        assert result.tools[0].description.en_US == "Tool description"