Fix title field preservation in tool transformations

Add title parameter to Tool.from_tool() and TransformedTool.from_tool()
to properly inherit or override title field when transforming tools.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/fastmcp/tools/tool.py

@@ -185,8 +185,9 @@ class Tool(FastMCPComponent):
         tool: Tool,
         transform_fn: Callable[..., Any] | None = None,
         name: str | None = None,
+        title: str | None | NotSetT = NotSet,
         transform_args: dict[str, ArgTransform] | None = None,
-        description: str | None = None,
+        description: str | None | NotSetT = NotSet,
         tags: set[str] | None = None,
         annotations: ToolAnnotations | None = None,
         output_schema: dict[str, Any] | None | Literal[False] = None,
@@ -199,6 +200,7 @@ class Tool(FastMCPComponent):
             tool=tool,
             transform_fn=transform_fn,
             name=name,
+            title=title,
             transform_args=transform_args,
             description=description,
             tags=tags,

src/fastmcp/tools/tool_transform.py

@@ -325,7 +325,8 @@ class TransformedTool(Tool):
         cls,
         tool: Tool,
         name: str | None = None,
-        description: str | None = None,
+        title: str | None | NotSetT = NotSet,
+        description: str | None | NotSetT = NotSet,
         tags: set[str] | None = None,
         transform_fn: Callable[..., Any] | None = None,
         transform_args: dict[str, ArgTransform] | None = None,
@@ -342,6 +343,7 @@ class TransformedTool(Tool):
                 to call the parent tool. Functions with **kwargs receive transformed
                 argument names.
             name: New name for the tool. Defaults to parent tool's name.
+            title: New title for the tool. Defaults to parent tool's title.
             transform_args: Optional transformations for parent tool arguments.
                 Only specified arguments are transformed, others pass through unchanged:
                 - Simple rename (str)
@@ -506,13 +508,18 @@ class TransformedTool(Tool):
                     f"{', '.join(sorted(duplicates))}"
                 )
 
-        final_description = description if description is not None else tool.description
+        final_name = name or tool.name
+        final_description = (
+            description if not isinstance(description, NotSetT) else tool.description
+        )
+        final_title = title if not isinstance(title, NotSetT) else tool.title
 
         transformed_tool = cls(
             fn=final_fn,
             forwarding_fn=forwarding_fn,
             parent_tool=tool,
-            name=name or tool.name,
+            name=final_name,
+            title=final_title,
             description=final_description,
             parameters=final_schema,
             output_schema=final_output_schema,

tests/tools/test_tool_transform.py

@@ -1316,3 +1316,88 @@ class TestTransformToolOutputSchema:
         # Should use ToolResult content directly
         assert result.content[0].text == "Direct: 6"  # type: ignore[attr-defined]
         assert result.structured_content == {"direct_value": 6, "doubled": 12}
+
+
+@pytest.fixture
+def sample_tool():
+    """Sample tool for testing transformations."""
+
+    def sample_func(x: int) -> str:
+        return f"Result: {x}"
+
+    return Tool.from_function(
+        sample_func,
+        name="sample_tool",
+        title="Original Tool Title",
+        description="Original description",
+    )
+
+
+@pytest.fixture
+def sample_tool_no_title():
+    """Sample tool without title for testing."""
+
+    def sample_func(x: int) -> str:
+        return f"Result: {x}"
+
+    return Tool.from_function(sample_func, name="no_title_tool")
+
+
+def test_transform_inherits_title(sample_tool):
+    """Test that transformed tools inherit title when none specified."""
+    transformed = Tool.from_tool(sample_tool)
+    assert transformed.title == "Original Tool Title"
+
+
+def test_transform_overrides_title(sample_tool):
+    """Test that transformed tools can override title."""
+    transformed = Tool.from_tool(sample_tool, title="New Tool Title")
+    assert transformed.title == "New Tool Title"
+
+
+def test_transform_sets_title_to_none(sample_tool):
+    """Test that transformed tools can explicitly set title to None."""
+    transformed = Tool.from_tool(sample_tool, title=None)
+    assert transformed.title is None
+
+
+def test_transform_inherits_none_title(sample_tool_no_title):
+    """Test that transformed tools inherit None title."""
+    transformed = Tool.from_tool(sample_tool_no_title)
+    assert transformed.title is None
+
+
+def test_transform_adds_title_to_none(sample_tool_no_title):
+    """Test that transformed tools can add title when parent has None."""
+    transformed = Tool.from_tool(sample_tool_no_title, title="Added Title")
+    assert transformed.title == "Added Title"
+
+
+def test_transform_inherits_description(sample_tool):
+    """Test that transformed tools inherit description when none specified."""
+    transformed = Tool.from_tool(sample_tool)
+    assert transformed.description == "Original description"
+
+
+def test_transform_overrides_description(sample_tool):
+    """Test that transformed tools can override description."""
+    transformed = Tool.from_tool(sample_tool, description="New description")
+    assert transformed.description == "New description"
+
+
+def test_transform_sets_description_to_none(sample_tool):
+    """Test that transformed tools can explicitly set description to None."""
+    transformed = Tool.from_tool(sample_tool, description=None)
+    assert transformed.description is None
+
+
+def test_transform_inherits_none_description(sample_tool_no_title):
+    """Test that transformed tools inherit None description."""
+    transformed = Tool.from_tool(sample_tool_no_title)
+    assert transformed.description is None
+
+
+def test_transform_adds_description_to_none(sample_tool_no_title):
+    """Test that transformed tools can add description when parent has None."""
+    transformed = Tool.from_tool(sample_tool_no_title, description="Added description")
+    assert transformed.description == "Added description"