In a Swarm team the tool call output of an agent is not transferred to the next agent.

[ekzhu]

Originally discovered via #5038

How to reproduce?

import asyncio
from datetime import datetime
from autogen_agentchat.agents import AssistantAgent
from autogen_agentchat.teams import Swarm
from autogen_agentchat.messages import HandoffMessage
from autogen_agentchat.ui import Console
from autogen_ext.models.openai import OpenAIChatCompletionClient
from autogen_agentchat.conditions import HandoffTermination, MaxMessageTermination


def execute_git_current_time():
    return datetime.now().strftime("%H:%M:%S")

def get_current_day():
    return datetime.now().strftime("%A")


async def main() -> None:
    model_client = OpenAIChatCompletionClient(model="gpt-4o")

    router = AssistantAgent(
        name="router",
        system_message="""You are a router agent that analyzes user questions and directs them to the appropriate agent.

        Your role is to:
        1. Analyze the user's input
        2. Determine if they're asking about:
            - handoff to time_agent for questions about time
            - handoff to day_agent for questions about date
        """,
        model_client=model_client,
        handoffs=["day_agent", "time_agent"],
    )

    time_agent = AssistantAgent(
        name="time_agent",
        system_message="""You are a time agent that provides the current time. Send the time information to the formatter agent.""",
        model_client=model_client,
        tools=[execute_git_current_time],
        handoffs=["formatter"],
    )

    day_agent = AssistantAgent(
        name="day_agent",
        system_message="""You are a day agent that provides the current day. Send the day information to the formatter agent.""",
        model_client=model_client,
        tools=[get_current_day],
        handoffs=["formatter"],
    )

    formatter = AssistantAgent(
        name="formatter",
        system_message="""You are a formatter agent that formats time and day information. Send the formatted information to the user.""",
        model_client=model_client,
        handoffs=["user"],
    )

    # Create a team with all agents
    handoff_termination = HandoffTermination(target="user")
    max_messages_termination = MaxMessageTermination(max_messages=100)
    termination = handoff_termination | max_messages_termination
    
    team = Swarm(
        participants=[router, time_agent, day_agent, formatter],
        termination_condition=termination,
    )

    await Console(team.run_stream(
       task=HandoffMessage(
            source="user",
            target="router",
            content="What time is it?",
       )
    ))

asyncio.run(main())

---------- user ----------
What time is it?
---------- router ----------
[FunctionCall(id='call_5KY9tHOOWodejGtz4nYYoL0R', arguments='{}', name='transfer_to_time_agent')]
---------- router ----------
[FunctionExecutionResult(content='Transferred to time_agent, adopting the role of time_agent immediately.', call_id='call_5KY9tHOOWodejGtz4nYYoL0R')]
---------- router ----------
Transferred to time_agent, adopting the role of time_agent immediately.
---------- time_agent ----------
[FunctionCall(id='call_NonawoVdSBG55rBC83cdBFiB', arguments='{}', name='execute_git_current_time'), FunctionCall(id='call_H77Mry5mJmoqCt6jkYjjAYX9', arguments='{}', name='transfer_to_formatter')]
---------- time_agent ----------
[FunctionExecutionResult(content='10:40:07', call_id='call_NonawoVdSBG55rBC83cdBFiB'), FunctionExecutionResult(content='Transferred to formatter, adopting the role of formatter immediately.', call_id='call_H77Mry5mJmoqCt6jkYjjAYX9')]
---------- time_agent ----------
Transferred to formatter, adopting the role of formatter immediately.
---------- formatter ----------
[FunctionCall(id='call_1zPjDwrcRMZggaJ84inYbjOg', arguments='{}', name='transfer_to_user')]
---------- formatter ----------
[FunctionExecutionResult(content='Transferred to user, adopting the role of user immediately.', call_id='call_1zPjDwrcRMZggaJ84inYbjOg')]
---------- formatter ----------
Transferred to user, adopting the role of user immediately.

You can see the tool call result of getting the current time is not transferred to the formatter in the handoff.

[ekzhu]

Note, this problem will still arise when parallel tool call is disabled, as the transfer message doesn't let agent reflect on the tool call.