fix: add explicit type annotation for call_tool decorator (modelcontextprotocol#1826)

Co-authored-by: Jay Hemnani <jayhemnani9910@gmail.com>
Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>

Author: 3 people

src/mcp/server/lowlevel/server.py

@@ -499,7 +499,7 @@ def call_tool(self, *, validate_input: bool = True):
 
         def decorator(
             func: Callable[
-                ...,
+                [str, dict[str, Any]],
                 Awaitable[
                     UnstructuredContent
                     | StructuredContent