Adds meta parameter and method for allowing information to be passed without intercepted by LLM

Author: iupadhyay

src/mcp/client/session.py

@@ -271,17 +271,22 @@ async def call_tool(
         self,
         name: str,
         arguments: dict[str, Any] | None = None,
+        meta: dict[str, Any] | None = None,
         read_timeout_seconds: timedelta | None = None,
         progress_callback: ProgressFnT | None = None,
     ) -> types.CallToolResult:
         """Send a tools/call request with optional progress callback support."""
+        request_meta = None
+        if meta:
+            request_meta = types.RequestParams.Meta(**meta)
 
         result = await self.send_request(
             types.ClientRequest(
                 types.CallToolRequest(
                     params=types.CallToolRequestParams(
                         name=name,
                         arguments=arguments,
+                        **({'_meta': request_meta} if request_meta else {}),
                     ),
                 )
             ),

src/mcp/server/fastmcp/server.py

@@ -1036,9 +1036,10 @@ def my_tool(x: int, ctx: Context) -> str:
         # Access resources
         data = ctx.read_resource("resource://data")
 
-        # Get request info
+        # Get request info and metadata
         request_id = ctx.request_id
         client_id = ctx.client_id
+        user_meta = ctx.request_meta
 
         return str(x)
     ```
@@ -1172,6 +1173,15 @@ def request_id(self) -> str:
         """Get the unique ID for this request."""
         return str(self.request_context.request_id)
 
+    @property
+    def request_meta(self) -> dict[str, Any]:
+        """Get the request metadata (hidden data passed from client)."""
+        if not self.request_context.meta:
+            return {}
+
+        meta_dict = self.request_context.meta.model_dump(exclude={'progressToken'})
+        return meta_dict
+
     @property
     def session(self):
         """Access to the underlying session for advanced usage."""