Add meta support to tool transformation utilities (#1295)

docs/patterns/tool-transformation.mdx

@@ -92,6 +92,7 @@ The `Tool.from_tool()` class method is the primary way to create a transformed t
 - `tags`: An optional set of tags for the new tool.
 - `annotations`: An optional set of `ToolAnnotations` for the new tool.
 - `serializer`: An optional function that will be called to serialize the result of the new tool.
+- `meta`: Control meta information for the tool. Use `None` to remove meta, any dict to set meta, or leave unset to inherit from parent.
 
 The result is a new `TransformedTool` object that wraps the parent tool and applies the transformations you specify. You can add this tool to your MCP server using its `add_tool()` method.
 
@@ -255,6 +256,50 @@ transform_args = {
 `default_factory` can only be used with `hide=True`. This is because visible parameters need static defaults that can be represented in a JSON schema for the client.
 </Warning>
 
+### Meta Information
+
+<VersionBadge version="2.11.0" />
+
+You can control meta information on transformed tools using the `meta` parameter. Meta information is additional data about the tool that doesn't affect its functionality but can be used by clients for categorization, routing, or other purposes.
+
+```python {15-17}
+from fastmcp import FastMCP
+from fastmcp.tools import Tool
+
+mcp = FastMCP()
+
+@mcp.tool
+def analyze_data(data: str) -> dict:
+    """Analyzes the provided data."""
+    return {"result": f"Analysis of {data}"}
+
+# Add custom meta information
+enhanced_tool = Tool.from_tool(
+    analyze_data,
+    name="enhanced_analyzer",
+    meta={
+        "category": "analytics",
+        "priority": "high",
+        "requires_auth": True
+    }
+)
+
+mcp.add_tool(enhanced_tool)
+```
+
+You can also remove meta information entirely:
+
+```python {6}
+# Remove meta information from parent tool
+simplified_tool = Tool.from_tool(
+    analyze_data,
+    name="simple_analyzer", 
+    meta=None  # Removes any meta information
+)
+```
+
+If you don't specify the `meta` parameter, the transformed tool inherits the parent tool's meta information.
+
 ### Required Values
 
 In rare cases where you want to make an optional argument required, you can set `required=True`. This has no effect if the argument was already required.
@@ -456,6 +501,10 @@ directly in the MCPConfig json file.
                 "weather_get_forecast": {
                     "name": "miami_weather",
                     "description": "Get the weather for Miami",
+                    "meta": {
+                        "category": "weather",
+                        "location": "miami"
+                    },
                     "arguments": {
                         "city": {
                             "name": "city",

src/fastmcp/tools/tool.py

@@ -208,6 +208,7 @@ class Tool(FastMCPComponent):
         annotations: ToolAnnotations | None = None,
         output_schema: dict[str, Any] | None | Literal[False] = None,
         serializer: Callable[[Any], str] | None = None,
+        meta: dict[str, Any] | None | NotSetT = NotSet,
         enabled: bool | None = None,
     ) -> TransformedTool:
         from fastmcp.tools.tool_transform import TransformedTool
@@ -223,6 +224,7 @@ class Tool(FastMCPComponent):
             annotations=annotations,
             output_schema=output_schema,
             serializer=serializer,
+            meta=meta,
             enabled=enabled,
         )
 

src/fastmcp/tools/tool_transform.py

@@ -366,6 +366,7 @@ class TransformedTool(Tool):
         annotations: ToolAnnotations | None = None,
         output_schema: dict[str, Any] | None | Literal[False] = None,
         serializer: Callable[[Any], str] | None = None,
+        meta: dict[str, Any] | None | NotSetT = NotSet,
         enabled: bool | None = None,
     ) -> TransformedTool:
         """Create a transformed tool from a parent tool.
@@ -390,6 +391,10 @@ class TransformedTool(Tool):
                 - dict: Use custom output schema
                 - False: Disable output schema and structured outputs
             serializer: New serializer. Defaults to parent's serializer.
+            meta: Control meta information:
+                - NotSet (default): Inherit from parent tool
+                - dict: Use custom meta information
+                - None: Remove meta information
 
         Returns:
             TransformedTool with the specified transformations.
@@ -546,6 +551,7 @@ class TransformedTool(Tool):
             description if not isinstance(description, NotSetT) else tool.description
         )
         final_title = title if not isinstance(title, NotSetT) else tool.title
+        final_meta = meta if not isinstance(meta, NotSetT) else tool.meta
 
         transformed_tool = cls(
             fn=final_fn,
@@ -559,6 +565,7 @@ class TransformedTool(Tool):
             tags=tags or tool.tags,
             annotations=annotations or tool.annotations,
             serializer=serializer or tool.serializer,
+            meta=final_meta,
             transform_args=transform_args,
             enabled=enabled if enabled is not None else True,
         )
@@ -851,6 +858,10 @@ class ToolTransformConfig(FastMCPBaseModel):
         default_factory=set,
         description="The new tags for the tool.",
     )
+    meta: dict[str, Any] | None = Field(
+        default=None,
+        description="The new meta information for the tool.",
+    )
 
     enabled: bool = Field(
         default=True,

tests/tools/test_tool_transform.py

@@ -13,7 +13,11 @@ from fastmcp.client.client import Client
 from fastmcp.exceptions import ToolError
 from fastmcp.tools import Tool, forward, forward_raw
 from fastmcp.tools.tool import FunctionTool, ToolResult
-from fastmcp.tools.tool_transform import ArgTransform, TransformedTool
+from fastmcp.tools.tool_transform import (
+    ArgTransform,
+    ToolTransformConfig,
+    TransformedTool,
+)
 
 
 def get_property(tool: Tool, name: str) -> dict[str, Any]:
@@ -1428,3 +1432,65 @@ 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"
+
+
+# Meta transformation tests
+def test_transform_inherits_meta(sample_tool):
+    """Test that transformed tools inherit meta when none specified."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    transformed = Tool.from_tool(sample_tool)
+    assert transformed.meta == {"original": True, "version": "1.0"}
+
+
+def test_transform_overrides_meta(sample_tool):
+    """Test that transformed tools can override meta."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    transformed = Tool.from_tool(sample_tool, meta={"custom": True, "priority": "high"})
+    assert transformed.meta == {"custom": True, "priority": "high"}
+
+
+def test_transform_sets_meta_to_none(sample_tool):
+    """Test that transformed tools can explicitly set meta to None."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    transformed = Tool.from_tool(sample_tool, meta=None)
+    assert transformed.meta is None
+
+
+def test_transform_inherits_none_meta(sample_tool_no_title):
+    """Test that transformed tools inherit None meta."""
+    sample_tool_no_title.meta = None
+    transformed = Tool.from_tool(sample_tool_no_title)
+    assert transformed.meta is None
+
+
+def test_transform_adds_meta_to_none(sample_tool_no_title):
+    """Test that transformed tools can add meta when parent has None."""
+    sample_tool_no_title.meta = None
+    transformed = Tool.from_tool(sample_tool_no_title, meta={"added": True})
+    assert transformed.meta == {"added": True}
+
+
+def test_tool_transform_config_inherits_meta(sample_tool):
+    """Test that ToolTransformConfig inherits meta when unset."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    config = ToolTransformConfig(name="config_tool")
+    transformed = config.apply(sample_tool)
+    assert transformed.meta == {"original": True, "version": "1.0"}
+
+
+def test_tool_transform_config_overrides_meta(sample_tool):
+    """Test that ToolTransformConfig can override meta."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    config = ToolTransformConfig(
+        name="config_tool", meta={"config": True, "priority": "high"}
+    )
+    transformed = config.apply(sample_tool)
+    assert transformed.meta == {"config": True, "priority": "high"}
+
+
+def test_tool_transform_config_removes_meta(sample_tool):
+    """Test that ToolTransformConfig can remove meta with None."""
+    sample_tool.meta = {"original": True, "version": "1.0"}
+    config = ToolTransformConfig(name="config_tool", meta=None)
+    transformed = config.apply(sample_tool)
+    assert transformed.meta is None