feat: add tool metadata in FastMCP.tool decorator (#1463)

Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

src/mcp/server/fastmcp/tools/base.py

@@ -34,6 +34,7 @@ class Tool(BaseModel):
     context_kwarg: str | None = Field(None, description="Name of the kwarg that should receive context")
     annotations: ToolAnnotations | None = Field(None, description="Optional annotations for the tool")
     icons: list[Icon] | None = Field(default=None, description="Optional list of icons for this tool")
+    meta: dict[str, Any] | None = Field(default=None, description="Optional metadata for this tool")
 
     @cached_property
     def output_schema(self) -> dict[str, Any] | None:
@@ -49,6 +50,7 @@ class Tool(BaseModel):
         context_kwarg: str | None = None,
         annotations: ToolAnnotations | None = None,
         icons: list[Icon] | None = None,
+        meta: dict[str, Any] | None = None,
         structured_output: bool | None = None,
     ) -> Tool:
         """Create a Tool from a function."""
@@ -81,6 +83,7 @@ class Tool(BaseModel):
             context_kwarg=context_kwarg,
             annotations=annotations,
             icons=icons,
+            meta=meta,
         )
 
     async def run(

src/mcp/server/fastmcp/tools/tool_manager.py

@@ -50,6 +50,7 @@ class ToolManager:
         description: str | None = None,
         annotations: ToolAnnotations | None = None,
         icons: list[Icon] | None = None,
+        meta: dict[str, Any] | None = None,
         structured_output: bool | None = None,
     ) -> Tool:
         """Add a tool to the server."""
@@ -60,6 +61,7 @@ class ToolManager:
             description=description,
             annotations=annotations,
             icons=icons,
+            meta=meta,
             structured_output=structured_output,
         )
         existing = self._tools.get(tool.name)