create_react_agent no run for ollama. Tool can not be call.

[DiamondLee12]

I want to build agents and firstly I tried examples

When I used AzureChatOpenAI(GPT4o), the agent can call tool to get the examples' result. However, when I used ollama, the tool could not be call and just got the json return. Is anyone has same problem?? Someone has any solution?

My code

from datetime import datetime
from langchain_openai import ChatOpenAI
from langgraph.prebuilt import create_react_agent
from langchain_core.prompts import ChatPromptTemplate
from langgraph.graph.message import add_messages
from langgraph.managed import IsLastStep
from typing_extensions import Annotated, TypedDict
from langgraph.checkpoint.memory import MemorySaver
from langchain_ollama import ChatOllama,OllamaLLM


local_llm = "llama3.2"

def check_weather(location: str, at_time: datetime | None = None) -> str:
    '''Return the weather forecast for the specified location.'''
    return f"It's always sunny in {location}"

tools = [check_weather]
llm = ChatOllama(model=local_llm, temperature=0,format="json")
graph = create_react_agent(llm, tools=tools,debug=True)
inputs = {"messages": [("user", "what's the weather in SF?")]}
for s in graph.stream(inputs, stream_mode="values"):
    message = s["messages"][-1]
    if isinstance(message, tuple):
        print(message)
    else:
        message.pretty_print()

When I used AzureChatOpenAI, I can get.

================================ Human Message =================================

what's the weather in SF?
INFO:httpx:HTTP Request: XX "HTTP/1.1 200 OK"
================================== Ai Message ==================================
Tool Calls:
check_weather (call_eYbdolAsRpvpMQrGmCEe7Et0)
Call ID: call_eYbdolAsRpvpMQrGmCEe7Et0
Args:
location: San Francisco, CA
================================= Tool Message =================================
Name: check_weather

It's always sunny in San Francisco, CA
INFO:httpx:HTTP Request: POST XX "HTTP/1.1 200 OK"
================================== Ai Message ==================================

The current weather in San Francisco, CA is sunny.

But When I used ollama(llama3.2, qwen2.5 etc. )

================================ Human Message =================================

what's the weather in SF?
INFO:httpx:HTTP Request: xxx "HTTP/1.1 200 OK"
================================== Ai Message ==================================

{"name": "check_weather", "parameters": {"location": "SF"}}