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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/fastmcp/tools/tool.py

@@ -197,13 +197,11 @@ def _convert_to_content(
             else:
                 other_content.append(item)
 
-        if len(other_content) == 1:
+        if other_content:
             other_content = _convert_to_content(
-                other_content[0], serializer=serializer, _process_as_single_item=True
-            )
-        elif len(other_content) > 1:
-            other_content = _convert_to_content(
-                other_content, serializer=serializer, _process_as_single_item=True
+                other_content[0] if len(other_content) == 1 else other_content,
+                serializer=serializer,
+                _process_as_single_item=True,
             )
 
         return other_content + mcp_types

tests/tools/test_tool.py

@@ -1,6 +1,6 @@
 import pytest
 from mcp.types import EmbeddedResource, ImageContent, TextContent, TextResourceContents
-from pydantic import AnyUrl, BaseModel
+from pydantic import AnyUrl
 
 from fastmcp import FastMCP, Image
 from fastmcp.client import Client
@@ -520,7 +520,7 @@ class TestConvertResultToContent:
         assert image_item.data == "ZmFrZWltYWdlZGF0YQ=="
 
     def test_list_of_mixed_types_list(self):
-        """Test that a list of mixed types is converted correctly."""
+        """Test that a list of mixed types, including a list as one of the elements, is converted correctly."""
         content1 = TextContent(type="text", text="hello")
         image_obj = Image(data=b"fakeimagedata")
         basic_data = [{"a": 1}, {"b": 2}]