Add meta to call tool

src/fastmcp/client/client.py

@@ -3,6 +3,7 @@
 import asyncio
 import copy
 import datetime
+import inspect
 import secrets
 from contextlib import AsyncExitStack, asynccontextmanager
 from dataclasses import dataclass, field
@@ -831,6 +832,7 @@ async def call_tool_mcp(
         arguments: dict[str, Any],
         progress_handler: ProgressHandler | None = None,
         timeout: datetime.timedelta | float | int | None = None,
+        meta: dict[str, Any] | None = None,
     ) -> mcp.types.CallToolResult:
         """Send a tools/call request and return the complete MCP protocol result.
 
@@ -842,6 +844,7 @@ async def call_tool_mcp(
             arguments (dict[str, Any]): Arguments to pass to the tool.
             timeout (datetime.timedelta | float | int | None, optional): The timeout for the tool call. Defaults to None.
             progress_handler (ProgressHandler | None, optional): The progress handler to use for the tool call. Defaults to None.
+            meta (dict[str, Any] | None, optional): Additional metadata to send with the tool call.
 
         Returns:
             mcp.types.CallToolResult: The complete response object from the protocol,
@@ -854,12 +857,32 @@ async def call_tool_mcp(
 
         if isinstance(timeout, int | float):
             timeout = datetime.timedelta(seconds=float(timeout))
-        result = await self.session.call_tool(
-            name=name,
-            arguments=arguments,
-            read_timeout_seconds=timeout,
-            progress_callback=progress_handler or self._progress_handler,
-        )
+
+        # Check if meta parameter is supported, remove this once MCP >= 1.19 is required
+        sig = inspect.signature(self.session.call_tool)
+        meta_supported = "meta" in sig.parameters
+
+        # Include meta parameter if supported, warn user if they tried to use it but it's not supported
+        if meta_supported:
+            result = await self.session.call_tool(
+                name=name,
+                arguments=arguments,
+                read_timeout_seconds=timeout,
+                progress_callback=progress_handler or self._progress_handler,
+                meta=meta,
+            )
+        else:
+            if meta is not None:
+                logger.warning(
+                    "The 'meta' parameter is not supported by your installed version of MCP. "
+                    "Please update to MCP >= 1.19 to use this feature. Proceeding without meta."
+                )
+            result = await self.session.call_tool(
+                name=name,
+                arguments=arguments,
+                read_timeout_seconds=timeout,
+                progress_callback=progress_handler or self._progress_handler,
+            )
         return result
 
     async def call_tool(
@@ -869,6 +892,7 @@ async def call_tool(
         timeout: datetime.timedelta | float | int | None = None,
         progress_handler: ProgressHandler | None = None,
         raise_on_error: bool = True,
+        meta: dict[str, Any] | None = None,
     ) -> CallToolResult:
         """Call a tool on the server.
 
@@ -879,6 +903,8 @@ async def call_tool(
             arguments (dict[str, Any] | None, optional): Arguments to pass to the tool. Defaults to None.
             timeout (datetime.timedelta | float | int | None, optional): The timeout for the tool call. Defaults to None.
             progress_handler (ProgressHandler | None, optional): The progress handler to use for the tool call. Defaults to None.
+            raise_on_error (bool, optional): Whether to raise a ToolError if the tool call results in an error. Defaults to True.
+            meta (dict[str, Any] | None, optional): Additional metadata to send with the tool call.
 
         Returns:
             CallToolResult:
@@ -898,6 +924,7 @@ async def call_tool(
             arguments=arguments or {},
             timeout=timeout,
             progress_handler=progress_handler,
+            meta=meta,
         )
         data = None
         if result.isError and raise_on_error: