diff --git a/gateway/platforms/api_server.py b/gateway/platforms/api_server.py
index 62196973d1..32c56d1fb5 100644
--- a/gateway/platforms/api_server.py
+++ b/gateway/platforms/api_server.py
@@ -1949,15 +1949,10 @@ class APIServerAdapter(BasePlatformAdapter):
                         "call_id": tc.get("id", ""),
                     })
             elif role == "tool":
-                output_content = msg.get("content", "")
-                if isinstance(output_content, list):
-                    output = output_content
-                else:
-                    output = [{"type": "input_text", "text": str(output_content)}]
                 items.append({
                     "type": "function_call_output",
                     "call_id": msg.get("tool_call_id", ""),
-                    "output": output,
+                    "output": msg.get("content", ""),
                 })
 
         # Final assistant message
diff --git a/tests/gateway/test_api_server.py b/tests/gateway/test_api_server.py
index 32346fc83d..8e3e066b8f 100644
--- a/tests/gateway/test_api_server.py
+++ b/tests/gateway/test_api_server.py
@@ -1547,7 +1547,7 @@ class TestToolCallsInOutput:
             assert output[0]["call_id"] == "call_abc123"
             assert output[1]["type"] == "function_call_output"
             assert output[1]["call_id"] == "call_abc123"
-            assert output[1]["output"] == [{"type": "input_text", "text": "42"}]
+            assert output[1]["output"] == "42"
             assert output[2]["type"] == "message"
             assert output[2]["content"][0]["text"] == "The result is 42."