This sample demonstrates how to use a remote Agent-to-Agent (A2A) agent as the root agent in the Agent Development Kit (ADK). This is a simplified approach where the main agent is actually a remote A2A service, also showcasing how to run remote agents using uvicorn command.

The A2A Root sample consists of:

• Root Agent (agent.py): A remote A2A agent proxy as root agent that talks to a remote a2a agent running on a separate server
• Remote Hello World Agent (remote_a2a/hello_world/agent.py): The actual agent implementation that handles dice rolling and prime number checking running on remote server

┌─────────────────┐    ┌────────────────────┐
│   Root Agent    │───▶│   Remote Hello     │
│ (RemoteA2aAgent)│    │   World Agent      │
│ (localhost:8000)│    │  (localhost:8001)  │
└─────────────────┘    └────────────────────┘

• The root_agent is a RemoteA2aAgent that connects to a remote A2A service
• Demonstrates how to use remote agents as the primary agent instead of local agents
• Shows the flexibility of the A2A architecture for distributed agent deployment

• The remote agent is served using uvicorn, a lightweight ASGI server
• Demonstrates a simple way to deploy A2A agents without using the ADK CLI
• Shows how to expose A2A agents as standalone web services

• Dice Rolling: Can roll dice with configurable number of sides
• Prime Number Checking: Can check if numbers are prime
• State Management: Maintains roll history in tool context
• Parallel Tool Execution: Can use multiple tools in parallel

• Uses the to_a2a() utility to convert a standard ADK agent to an A2A service
• Minimal configuration required for remote agent deployment

1. Start the Remote A2A Agent server:

   # Start the remote agent using uvicorn
   uvicorn contributing.samples.a2a_root.remote_a2a.hello_world.agent:a2a_app --host localhost --port 8001

2. Run the Main Agent:

   # In a separate terminal, run the adk web server
   adk web contributing/samples/

Once both services are running, you can interact with the root agent:

Simple Dice Rolling:

User: Roll a 6-sided die
Bot: I rolled a 4 for you.

Prime Number Checking:

User: Is 7 a prime number?
Bot: Yes, 7 is a prime number.

Combined Operations:

User: Roll a 10-sided die and check if it's prime
Bot: I rolled an 8 for you.
Bot: 8 is not a prime number.

Multiple Rolls with Prime Checking:

User: Roll a die 3 times and check which results are prime
Bot: I rolled a 3 for you.
Bot: I rolled a 7 for you.
Bot: I rolled a 4 for you.
Bot: 3, 7 are prime numbers.

• root_agent: A RemoteA2aAgent that connects to the remote A2A service
• Agent Card URL: Points to the well-known agent card endpoint on the remote server

• roll_die(sides: int): Function tool for rolling dice with state management
• check_prime(nums: list[int]): Async function for prime number checking
• root_agent: The main agent with comprehensive instructions
• a2a_app: The A2A application created using to_a2a() utility

Connection Issues:

• Ensure the uvicorn server is running on port 8001
• Check that no firewall is blocking localhost connections
• Verify the agent card URL in the root agent configuration
• Check uvicorn logs for any startup errors

Agent Not Responding:

• Check the uvicorn server logs for errors
• Verify the agent instructions are clear and unambiguous
• Ensure the A2A app is properly configured with the correct port

Uvicorn Issues:

• Make sure the module path is correct: contributing.samples.a2a_root.remote_a2a.hello_world.agent:a2a_app
• Check that all dependencies are installed