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

"Could not get parameter" Error
- Ensure all required parameters have default values
- Check node configuration and connections
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
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
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

Fork the repository
Create a feature branch
Make your changes
Add tests if applicable
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:

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

Package detail

n8n-nodes-a2a-protocol

readme