A2A Server Setup

Agent Zero can communicate with other Agent Zero instances using the A2A (Agent-to-Agent) protocol based on FastA2A. This guide shows you how to enable and configure A2A connectivity through the Settings UI.

What is A2A?

A2A enables direct communication between multiple Agent Zero instances. This allows:

• Distributed workflows - Delegate tasks to specialized agent instances
• Context isolation - Maintain separate workspaces for different agents
• Long-running collaboration - Persistent agent-to-agent conversations
• Project-specific delegation - Route work to agents with specific project contexts

[!NOTE] This guide covers enabling Agent Zero as an A2A server. For API-level integration details, see the advanced connectivity documentation.

Enabling the A2A Server

Step 1: Open A2A Configuration

1. Click Settings in the sidebar
2. Navigate to the MCP/A2A tab
3. Scroll to the A0 A2A Server section
4. Toggle Enable A2A server to ON

Step 2: Get Connection URL

1. Click on connection example to view your A2A connection details
2. The dialog displays:
   • API Token - Automatically generated from your username and password
   • A2A Connection URL - The full URL other agents will use to connect
   • Optional Project selector - To create project-specific connection URLs

Step 3: Save Configuration

1. Click Save to apply your settings
2. The A2A server is now active and ready to accept connections

[!IMPORTANT] The API token changes when you update your Agent Zero credentials. Existing connections will need to be reconfigured with the new token.

Connection URL Format

The basic A2A connection URL follows this format:

http://YOUR_HOST:PORT/a2a/t-YOUR_API_TOKEN

With Project Context

To connect with a specific project active:

http://YOUR_HOST:PORT/a2a/t-YOUR_API_TOKEN/p-PROJECT_NAME

When a project is specified:

• All A2A conversations run in that project's context
• The agent has access to project-specific resources and knowledge
• Enables isolated, project-focused agent collaboration

Example Use Cases

1. Local Development Setup

Two Agent Zero instances on the same machine:

Instance 1: http://localhost:8080/a2a/t-abc123xyz
Instance 2: http://localhost:8081/a2a/t-def456uvw

2. Remote Agent Collaboration

Connect to a remote Agent Zero instance:

http://agent.example.com:8080/a2a/t-remote-token

3. Project-Specific Delegation

Main agent delegates frontend work to specialized agent:

http://localhost:8081/a2a/t-frontend-token/p-webapp-ui

Docker Networking

If running Agent Zero in Docker:

• Same Host: Use host.docker.internal:PORT (macOS/Windows) or container networking (Linux)
• Different Hosts: Use the public IP or domain name of the target instance
• Port Mapping: Ensure the Agent Zero port is exposed in your Docker configuration

Security Considerations

• Token Protection: Keep your API tokens secure - they provide full access to your Agent Zero instance
• Network Access: Consider using firewalls or reverse proxies to restrict A2A endpoint access
• HTTPS: For production deployments, use HTTPS to encrypt A2A communication
• Credential Rotation: Changing your password will invalidate all existing A2A connection URLs

Testing Your Connection

You can test A2A connectivity using curl:

curl -X POST http://localhost:8080/a2a/t-YOUR_TOKEN \
  -H "Content-Type: application/json" \
  -d '{"message": "Hello from another agent"}'

A2A vs MCP

[!TIP] Use A2A when you need another agent's reasoning and conversation capabilities. Use MCP when you just need access to specific tools or functions.

Troubleshooting

Connection Refused

• Verify the A2A server is enabled in Settings
• Check that the Agent Zero instance is running
• Confirm the port is accessible (check firewall rules)

Invalid Token

• Token may have changed due to credential updates
• Generate a new connection URL from Settings > MCP/A2A
• Update the connecting agent's configuration

Project Not Found

• Verify the project name in the URL matches exactly
• Check that the project exists in the target instance
• Project names are case-sensitive

Advanced Configuration

For detailed A2A protocol specifications, API examples, and integration patterns, see the Advanced Connectivity Guide.