diff --git a/src/fastmcp/tools/tool_manager.py b/src/fastmcp/tools/tool_manager.py
index 3114fa1ae..509f4e6de 100644
--- a/src/fastmcp/tools/tool_manager.py
+++ b/src/fastmcp/tools/tool_manager.py
@@ -106,7 +106,7 @@ class ToolManager:
         if key in self._tools:
             del self._tools[key]
         else:
-            raise NotFoundError(f"Tool {key!r} not found.")
+            raise NotFoundError(f"Unknown tool: {key}")
 
     async def call_tool(
         self, key: str, arguments: dict[str, Any]
diff --git a/tests/tools/test_tool_manager.py b/tests/tools/test_tool_manager.py
index 4d61d0520..9d35d177f 100644
--- a/tests/tools/test_tool_manager.py
+++ b/tests/tools/test_tool_manager.py
@@ -117,7 +117,7 @@ class TestAddTools:
     def test_remove_tool_missing_key(self):
         """Test removing a tool that does not exist raises NotFoundError."""
         manager = ToolManager()
-        with pytest.raises(NotFoundError, match="Tool 'missing' not found"):
+        with pytest.raises(NotFoundError, match=f"Unknown tool: {'missing'}"):
             manager.remove_tool("missing")
 
     def test_warn_on_duplicate_tools(self, caplog):