Cherry-pick prebuilt (#5204)

fix: [prebuilt] Checks for pre-bound model with builtin tools (#5203)

libs/prebuilt/langgraph/prebuilt/chat_agent_executor.py

@@ -140,7 +140,9 @@ def _get_prompt_runnable(prompt: Optional[Prompt]) -> Runnable:
     return prompt_runnable
 
 
-def _should_bind_tools(model: LanguageModelLike, tools: Sequence[BaseTool]) -> bool:
+def _should_bind_tools(
+    model: LanguageModelLike, tools: Sequence[BaseTool], num_builtin: int = 0
+) -> bool:
     if isinstance(model, RunnableSequence):
         model = next(
             (
@@ -158,9 +160,10 @@ def _should_bind_tools(model: LanguageModelLike, tools: Sequence[BaseTool]) -> b
         return True
 
     bound_tools = model.kwargs["tools"]
-    if len(tools) != len(bound_tools):
+    if len(tools) != len(bound_tools) - num_builtin:
         raise ValueError(
             "Number of tools in the model.bind_tools() and tools passed to create_react_agent must match"
+            f" Got {len(tools)} tools, expected {len(bound_tools) - num_builtin}"
         )
 
     tool_names = set(tool.name for tool in tools)
@@ -444,9 +447,8 @@ def create_react_agent(
     tool_calling_enabled = len(tool_classes) > 0
 
     if (
-        _should_bind_tools(model, tool_classes)
+        _should_bind_tools(model, tool_classes, num_builtin=len(llm_builtin_tools))
         and len(tool_classes) > 0
-        or (len(llm_builtin_tools) > 0)
     ):
         model = cast(BaseChatModel, model).bind_tools(tool_classes + llm_builtin_tools)  # type: ignore[operator]
 

libs/prebuilt/tests/model.py

@@ -73,9 +73,12 @@ class FakeToolCallingModel(BaseChatModel):
 
         tool_dicts = []
         for tool in tools:
+            if isinstance(tool, dict):
+                tool_dicts.append(tool)
+                continue
             if not isinstance(tool, BaseTool):
                 raise TypeError(
-                    "Only BaseTool is supported by FakeToolCallingModel.bind_tools"
+                    "Only BaseTool and dict is supported by FakeToolCallingModel.bind_tools"
                 )
 
             # NOTE: this is a simplified tool spec for testing purposes only

libs/prebuilt/tests/test_react_agent.py

@@ -275,7 +275,8 @@ async def test_prompt_with_store_async():
 
 @pytest.mark.parametrize("tool_style", ["openai", "anthropic"])
 @pytest.mark.parametrize("version", REACT_TOOL_CALL_VERSIONS)
-def test_model_with_tools(tool_style: str, version: str):
+@pytest.mark.parametrize("include_builtin", [True, False])
+def test_model_with_tools(tool_style: str, version: str, include_builtin: bool):
     model = FakeToolCallingModel(tool_style=tool_style)
 
     @dec_tool
@@ -288,10 +289,27 @@ def test_model_with_tools(tool_style: str, version: str):
         """Tool 2 docstring."""
         return f"Tool 2: {some_val}"
 
+    tools = [tool1, tool2]
+    if include_builtin:
+        tools.append(
+            {
+                "type": "mcp",
+                "server_label": "atest_sever",
+                "server_url": "https://some.mcp.somewhere.com/sse",
+                "headers": {"foo": "bar"},
+                "allowed_tools": [
+                    "mcp_tool_1",
+                    "set_active_account",
+                    "get_url_markdown",
+                    "get_url_screenshot",
+                ],
+                "require_approval": "never",
+            }
+        )
     # check valid agent constructor
     agent = create_react_agent(
-        model.bind_tools([tool1, tool2]),
-        [tool1, tool2],
+        model.bind_tools(tools),
+        tools,
         version=version,
     )
     result = agent.nodes["tools"].invoke(