Automate Event Planning - The crew must end with at most one asynchronous task

Short Course Q&A Multi AI Agent Systems with crewAI
1

Hi! I’m getting this error when I try to create the Crew as it is in the notebook.

ValidationError: 1 validation error for Crew
  The crew must end with at most one asynchronous task. [type=async_task_count, input_value={'agents': [Agent(role=Ve...own.)], 'verbose': True}, input_type=dict]

I’m using the crewAI version 0.51.1. I know it is a different version compared to the one in the sandbox lab. But I’d like to understand what I need to change to make it work.

My agents:

venue_coordinator = Agent(
    role="Venue Coordinator",
    goal="Identify and book an appropriate venue "
    "based on event requirements",
    tools=[search_tool, scrape_tool],
    verbose=True,
    backstory=(
        "With a keen sense of space and "
        "understanding of event logistics, "
        "you excel at finding and securing "
        "the perfect venue that fits the event's theme, "
        "size, and budget constraints."
    )
)

 # Agent 2: Logistics Manager
logistics_manager = Agent(
    role='Logistics Manager',
    goal=(
        "Manage all logistics for the event "
        "including catering and equipmen"
    ),
    tools=[search_tool, scrape_tool],
    verbose=True,
    backstory=(
        "Organized and detail-oriented, "
        "you ensure that every logistical aspect of the event "
        "from catering to equipment setup "
        "is flawlessly executed to create a seamless experience."
    )
)

# Agent 3: Marketing and Communications Agent
marketing_communications_agent = Agent(
    role="Marketing and Communications Agent",
    goal="Effectively market the event and "
         "communicate with participants",
    tools=[search_tool, scrape_tool],
    verbose=True,
    backstory=(
        "Creative and communicative, "
        "you craft compelling messages and "
        "engage with potential attendees "
        "to maximize event exposure and participation."
    )
)

Taks

venue_task = Task(
    description="Find a venue in {event_city} "
                "that meets criteria for {event_topic}.",
    expected_output="All the details of a specifically chosen"
                    "venue you found to accommodate the event.",
    human_input=True,
    output_json=VenueDetails,
    output_file="venue_details.json",  
      # Outputs the venue details as a JSON file
    agent=venue_coordinator
)

logistics_task = Task(
    description="Coordinate catering and "
                 "equipment for an event "
                 "with {expected_participants} participants "
                 "on {tentative_date}.",
    expected_output="Confirmation of all logistics arrangements "
                    "including catering and equipment setup.",
    human_input=True,
    async_execution=True,
    agent=logistics_manager
)

marketing_task = Task(
    description="Promote the {event_topic} "
                "aiming to engage at least"
                "{expected_participants} potential attendees.",
    expected_output="Report on marketing activities "
                    "and attendee engagement formatted as markdown.",
    async_execution=True,
    output_file="marketing_report.md",  # Outputs the report as a text file
    agent=marketing_communications_agent
)

Crew

# Define the crew with agents and tasks
event_management_crew = Crew(
    agents=[venue_coordinator, 
            logistics_manager, 
            marketing_communications_agent],
    
    tasks=[venue_task, 
           logistics_task, 
           marketing_task],
    
    verbose=True
)