diff --git a/backend/api/chat_router.py b/backend/api/chat_router.py
index 2ca43b8..84aa407 100644
--- a/backend/api/chat_router.py
+++ b/backend/api/chat_router.py
@@ -5,6 +5,7 @@
 """
 from __future__ import annotations
 
+import functools
 import json
 import os
 from datetime import datetime, timezone
@@ -680,16 +681,27 @@ def _wrap_mcp_tool_safe(tool):
     这样 LangChain Agent 在工具调用失败时仍能写入对应的 ToolMessage，
     保持 checkpoint 中消息历史的完整性，避免下次对话因 tool_calls 缺少
     配对回复而触发 LLM 400 BadRequest 错误。
+
+    langchain_mcp_adapters 生成的工具使用 response_format='content_and_artifact'，
+    _arun 必须返回 (content, artifact) 元组，不能返回裸字符串。
     """
     original_arun = tool._arun
+    expects_tuple = getattr(tool, "response_format", "content") == "content_and_artifact"
 
+    def _as_tool_result(content):
+        return (content, None) if expects_tuple else content
+
+    @functools.wraps(original_arun)
     async def safe_arun(*args, **kwargs):
         try:
-            return await original_arun(*args, **kwargs)
+            result = await original_arun(*args, **kwargs)
+            if expects_tuple and not isinstance(result, tuple):
+                return _as_tool_result(result)
+            return result
         except Exception as exc:
             error_msg = f"工具 [{tool.name}] 调用失败: {exc}"
             logger.warning(f"MCP 工具异常已捕获，返回错误字符串以维持对话完整性: {error_msg}")
-            return error_msg
+            return _as_tool_result(error_msg)
 
     tool._arun = safe_arun
     return tool
diff --git a/mcp-server-demo/Dockerfile b/mcp-server-demo/Dockerfile
index 31ceecf..4fa16db 100644
--- a/mcp-server-demo/Dockerfile
+++ b/mcp-server-demo/Dockerfile
@@ -8,15 +8,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY pyproject.toml ./
 COPY excel_analyzer.py server.py ./
 
-RUN pip install --no-cache-dir --upgrade pip -timeout 120 --retries 10 \
-    && pip install --no-cache-dir  -timeout 120 --retries 10\
-        "mcp>=1.27.2" \
-        "python-dotenv>=1.0.0" \
-        "httpx>=0.28.0" \
-        "uvicorn>=0.48.0" \
-        "pandas>=2.0.0" \
-        "openpyxl>=3.1.0" \
-        "xlrd>=2.0.1"
+RUN pip install --no-cache-dir --upgrade pip \
+    && pip install --no-cache-dir --timeout 120 --retries 10 .
 
 ENV MCP_HOST=0.0.0.0
 ENV MCP_PORT=8010