Handler

Handler is an open-source A2A Protocol
client and developer toolkit.

It provides a CLI and TUI for communicating with remote agents, an MCP server
for bridging AI assistants into the A2A ecosystem, a reference server agent
implementation, push notification support, and agent card validation. Whether
you're building agents, integrating with existing ones, or exploring
agent-to-agent communication, Handler gives you the observability and control
you need from your terminal.

Who is Handler For?

Handler is for developers, researchers, and teams working with AI agents. If
you're building agents that speak A2A, Handler helps you test and debug them. If
you're integrating with existing A2A agents, Handler gives you a fast way to
explore their capabilities. If you want your AI assistant to communicate with
other agents, Handler's MCP server bridges that gap. And if you're just curious
about agent-to-agent communication, Handler is a great place to start.

Get Started

Install

Install with uv:

uv tool install a2a-handler

Or with pipx:

pipx install a2a-handler

Or with pip:

pip install a2a-handler

Run

Or, run from an ephemeral environment:

# With uv
uvx --from a2a-handler handler

# With pipx
pipx run a2a-handler

Development Environment

A hermetically sealed
development environment is available with
Nix:

nix develop

This provides Python, uv, and just with all commands ready to use.

For usage documentation, see the
Handler docs.

Contributing

See CONTRIBUTING.md.