add mcp use method

examples/mcp_modes/direct_tool_loop.py

@@ -0,0 +1,52 @@
+# examples/mcp_modes/direct_tool_loop.py
+import asyncio
+from langchain_core.messages import HumanMessage, ToolMessage
+from langgraph_qwen.chat_model import ChatQwenOpenAICompat
+from langgraph_qwen.mcp import load_mcp_tools
+
+PHASE1_SERVERS = {
+    "math": {"command":"python","args":["/abs/path/to/math_server.py"],"transport":"stdio"}
+}
+PHASE2_SERVERS = {
+    "weather": {"url":"http://127.0.0.1:8000/mcp/","transport":"streamable_http"}
+}
+
+async def main(max_steps: int = 8):
+    # ★ 比如不同阶段加载不同工具集
+    tools_phase1 = await load_mcp_tools(servers=PHASE1_SERVERS)
+    tools_phase2 = await load_mcp_tools(servers=PHASE2_SERVERS)
+
+    model = ChatQwenOpenAICompat(temperature=0).bind_tools(
+        tools_phase1 + tools_phase2
+    ).bind(tool_choice="auto")
+
+    tool_map = {t.name: t for t in (tools_phase1 + tools_phase2)}
+    msgs = [HumanMessage(content="先用数学工具算 12*(3+5)，再查北京天气，最后给一句总结。")]
+
+    for _ in range(max_steps):
+        ai = await model.ainvoke(msgs)
+        msgs.append(ai)
+        calls = getattr(ai, "tool_calls", []) or ai.additional_kwargs.get("tool_calls", [])
+        if not calls:
+            break
+        for call in calls:
+            name, args, call_id = call.get("name"), call.get("args", {}), call.get("id") or ""
+            tool = tool_map.get(name)
+            if not tool:
+                msgs.append(ToolMessage(tool_call_id=call_id, content=f"Unknown tool: {name}"))
+                continue
+            try:
+                if hasattr(tool, "ainvoke"):
+                    out = await tool.ainvoke(args)
+                else:
+                    out = tool.invoke(args)
+                msgs.append(ToolMessage(tool_call_id=call_id, content=str(out)))
+            except Exception as e:
+                msgs.append(ToolMessage(tool_call_id=call_id, content=f"Error: {e}"))
+
+    final = await model.ainvoke(msgs)
+    print("=== Final ===")
+    print(final.content)
+
+if __name__ == "__main__":
+    asyncio.run(main())