N8N A2A Protocol Nodes

A collection of n8n custom nodes implementing the Agent-to-Agent (A2A) Protocol for enabling agent interoperability and communication within n8n workflows.

Overview

This package provides a complete set of n8n nodes for implementing A2A Protocol communication:

• A2A Agent Registry - Central registry for agent discovery and management
• A2A Remote Agent Server - Server node that receives and processes A2A tasks
• A2A Client Agent - Client node for sending tasks to remote A2A agents
• A2A Client Tool - 🆕 NEW! MCP-compatible tool for seamless agent communication
• A2A Callback - Enhanced callback node for returning results to A2A servers

Features

✅ Full A2A Protocol Compliance - Implements A2A v1.0 specification
✅ MCP Integration - 🆕 NEW! Model Context Protocol compatibility with usableAsTool: true
✅ Synchronous & Asynchronous Processing - Support for both sync and async workflows
✅ Agent Discovery - Automatic agent registration and discovery
✅ Workflow Integration - Native n8n workflow compatibility
✅ Flexible Callback System - Multiple callback URL resolution methods
✅ Enhanced Debugging - Comprehensive logging and error reporting
✅ Clean Console Output - Minimal logging in production (debug available in callback node)

Installation

NPM Installation (Recommended)

# Install the community node package
npm install -g n8n-nodes-a2a-protocol

# Start n8n (nodes auto-load)
n8n start

That's it! The A2A Protocol nodes will automatically appear in your n8n interface.

Local Development Installation

For local development and testing:

# Clone and install locally
git clone https://github.com/Vinoth-Paulraj-HID/n8n-a2a-protocol.git
cd n8n-a2a-protocol/n8n
npm install
npm run build

# Install globally from local project folder
npm install -g .

# Start n8n
n8n start

Development/Source Installation

git clone https://github.com/Vinoth-Paulraj-HID/n8n-a2a-protocol.git
cd n8n-a2a-protocol/n8n
npm install
npm run build
npm install -g .

Usage

Using A2A Nodes (After npm Installation)

After installing via npm, the nodes are automatically available in n8n:

# Simply start n8n - nodes are auto-discovered
n8n start

No environment variables needed! The nodes will appear in your n8n node palette under:

• Triggers: A2A Agent Registry, A2A Remote Agent Server
• Regular: A2A Client Agent, A2A Callback
• Transform: A2A Client Tool 🆕 NEW!

MCP Integration Setup

For MCP Server Trigger compatibility:

# Enable community package tool usage
export N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE="true"
n8n start

# Windows PowerShell
$env:N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE="true"
n8n start

Manual/Development Setup Only

⚠️ Only needed for local development or manual installation:

# Set custom extensions path (development only)
export N8N_CUSTOM_EXTENSIONS="/path/to/n8n-nodes-a2a-protocol"
n8n start

# Windows PowerShell (development only)
$env:N8N_CUSTOM_EXTENSIONS="C:\path\to\n8n-nodes-a2a-protocol"
n8n start

Node Documentation

A2A Client Tool 🆕 NEW!

MCP-compatible tool for seamless A2A agent communication:

• MCP Integration: usableAsTool: true enables MCP Server Trigger discovery
• Agent Discovery: Automatic A2A agent discovery via registry
• Message Integration: Enhanced message handling in both top-level params and data payload
• Processing Modes: Sync/async processing with configurable timeout
• Registry Support: Auto-populated local servers with fallback to manual entry
• JSON-RPC 2.0: Full A2A protocol compliance with enhanced error handling

Perfect for MCP workflows:

[MCP Client] → [MCP Server Trigger] → [A2A Client Tool] → [A2A Remote Agent Server]

A2A Remote Agent Server

Acts as a trigger node that receives A2A tasks and forwards them to your n8n workflow:

• Port: 7000 (default)
• Processing Modes: sync, async, mixed
• Auto-registration: Registers with A2A Registry automatically

A2A Callback

Enhanced callback node with multiple URL resolution methods:

• Auto-detect: Automatically finds callback URL from A2A Server data
• Expression: Use n8n expressions like {{ $("A2A Agent Server").item.json._workflow_instructions.callback_url}}
• Manual: Manually specify callback URLs

A2A Agent Registry

Central registry for agent discovery:

• Port: 8080 (default)
• Health Monitoring: Tracks agent availability
• Discovery API: RESTful API for agent lookup

A2A Client Agent

Send tasks to remote A2A agents:

• Target Selection: Manual or registry-based agent discovery
• Processing Modes: Support for sync/async requests
• Error Handling: Comprehensive error reporting

Configuration Examples

Basic MCP Workflow 🆕 NEW!

[MCP Server Trigger] → [A2A Client Tool] → [Process Response]

Basic Sync Workflow

A2A Remote Agent Server → Your Processing → A2A Callback

Advanced Workflow with Agent Discovery

A2A Agent Registry → A2A Client Agent → Process Response

MCP + A2A Integration

[MCP Client] → [MCP Server Trigger] → [A2A Client Tool] → [A2A Remote Agent Server] → [Processing] → [A2A Callback]

Troubleshooting

Common Issues

1. "Could not get parameter" Error

   • Ensure all required parameters have default values
   • Check node configuration and connections

2. Callback URL Not Found

   • Verify A2A Server node is connected and configured
   • Use "From Node Expression" mode in A2A Callback
   • Check the exact node name in your workflow

3. MCP Tool Not Discoverable 🆕

   • Ensure N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE="true" is set
   • Verify the tool appears in the "Transform" section
   • Check that usableAsTool: true is properly configured

4. Port Already in Use

   • Change port numbers in node configuration
   • Stop existing A2A processes

Debug Mode

The A2A Callback node includes comprehensive debugging:

• Set callbackUrlSource to expression to see available nodes
• Check console output for detailed field information
• Verify node names and data structures

Development

Building

npm run build

Development Mode

npm run dev

Linting

npm run lint
npm run lintfix

Architecture

┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
│   A2A Client    │───▶│  A2A Registry    │◀───│  A2A Server     │
│     Agent       │    │                  │    │                 │
└─────────────────┘    └──────────────────┘    └─────────────────┘
                                                         │
                              🆕 NEW MCP FLOW            ▼
┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
│   MCP Client    │───▶│ MCP Server Trigger│───▶│ A2A Client Tool │
│                 │    │                  │    │                 │
└─────────────────┘    └──────────────────┘    └─────────────────┘
                                                         │
                                                         ▼
                                              ┌─────────────────┐
                                              │  N8N Workflow   │
                                              │   Processing    │
                                              └─────────────────┘
                                                         │
                                                         ▼
                                              ┌─────────────────┐
                                              │  A2A Callback   │
                                              │    Response     │
                                              └─────────────────┘

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests if applicable
5. Submit a pull request

License

MIT License - see LICENSE file for details

Version History

v1.1.0 🆕 NEW!

• Major Enhancement: Added A2A Client Tool with MCP integration
• MCP Compatibility: Implements usableAsTool: true for MCP Server Trigger discovery
• Enhanced Agent Discovery: Dynamic agent discovery with registry integration
• Message Integration: Dual message placement in both top-level params and data payload
• JSON-RPC 2.0: Full A2A protocol compliance with enhanced error handling
• Local Installation: Added npm install -g . command for local development
• Tool Pattern: Follows standard n8n tool pattern with group: ['transform']

v1.0.0

• Initial release with full A2A Protocol support
• All four core nodes implemented
• Enhanced callback system with expression support
• Comprehensive debugging and error handling
• Clean console output (removed verbose logging from server nodes)

Support

For issues and questions:

1. Check the troubleshooting section above
2. Enable debug mode in A2A Callback node
3. Review console output for detailed error information
4. Submit issues with complete debug logs