Handler

Handler is an open-source A2A protocol client for software engineers building, testing, and operating agentic systems. It provides an interactive TUI, a scriptable CLI with structured output, and an MCP server that lets other agents integrate with A2A services directly. Handler also supports global and repo-scoped A2A server configuration with bearer, API key, mTLS, and OAuth2 client credentials auth.

Install

Install Handler from the PyPI package as a uv tool:

uv tool install a2a-handler

Or with pipx:

pipx install a2a-handler

Or with pip:

pip install a2a-handler

Quick Start

Open the interactive terminal UI:

handler tui

Inspect an A2A server's agent card:

handler card get --url http://localhost:8000

Send a message from the CLI:

handler message send --url URL --text "hello"

Open the full documentation:

handler docs

Run Without Installing

Run Handler with uvx:

uvx --from a2a-handler handler

Run Handler with pipx:

pipx run a2a-handler

Documentation

Read the documentation at https://handler.alduncanson.com.