fix(dspy): return MCP text blocks even when the only one is empty

_convert_mcp_tool_result chose between text and non-text content with
`tool_content or non_text_contents`. A single text block collapses to its
string, so one empty block read as falsy and the result fell through to
the image, while two empty blocks returned ['', '']. Key the choice on
whether any text block exists, so text wins in both cases.

Author: chrikrah

dspy/utils/mcp.py

@@ -48,7 +48,7 @@ def _convert_mcp_tool_result(
     if result_mode == "structured" and _field_is_set(call_tool_result, "structured_content", "structuredContent"):
         return _get_field(call_tool_result, "structured_content", "structuredContent")
 
-    return tool_content or non_text_contents
+    return tool_content if text_contents else non_text_contents
 
 
 def convert_mcp_tool(

tests/utils/test_mcp.py

@@ -65,6 +65,25 @@ def test_structured_result_mode_returns_every_json_value_exactly(field_style, st
     assert type(converted) is type(structured)
 
 
+@pytest.mark.extra
+@pytest.mark.parametrize("result_mode", ["text", "structured"])
+@pytest.mark.parametrize(
+    ("texts", "expected"),
+    [
+        pytest.param(["chart"], "chart", id="one-text"),
+        pytest.param([""], "", id="one-empty-text"),
+        pytest.param(["", ""], ["", ""], id="two-empty-texts"),
+    ],
+)
+def test_text_blocks_win_over_images_even_when_empty(result_mode, texts, expected):
+    from mcp.types import CallToolResult, ImageContent, TextContent
+
+    image = ImageContent(type="image", data="iVBORw0KGgo=", mimeType="image/png")
+    content = [TextContent(type="text", text=text) for text in texts] + [image]
+
+    assert _convert_mcp_tool_result(CallToolResult(content=content), result_mode=result_mode) == expected
+
+
 @pytest.mark.extra
 @pytest.mark.parametrize("field_style", ["camel", "snake"])
 def test_structured_result_mode_falls_back_when_field_is_absent(field_style):