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, HTTP Basic, mTLS, OAuth2 client credentials, and OpenID Connect auth.
Features
- Streams replies as they arrive, in the TUI and the CLI, and can stop a running task or answer an agent that pauses for input
- Sends text, files (inline or by URL), and structured data, and shows the file and data parts agents send back
- Lists, inspects, cancels, and resubscribes to tasks, and manages push notification configs with a bundled local webhook receiver
- Speaks JSON-RPC and HTTP+JSON out of the box, gRPC with the
grpcextra, and lets the agent card pick the transport - Requests A2A extensions and fetches the extended card an agent offers to authenticated clients
- Keeps credentials on the origin you configured, never on a host an agent card happens to name
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"
Stream the reply, with a file attached:
handler message stream --url URL --text "Review this" --file ./report.pdf
List the agent's tasks:
handler task list --url URL
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.
For coding agents
The docs ship as an agent skill, regenerated on every deploy. Install it into
Claude Code, Cursor, Windsurf, or any agent that reads the SKILL.md format:
npx skills add https://handler.alduncanson.com
Or fetch it by hand from https://handler.alduncanson.com/skill.md. For live lookups, agents can also use the hosted documentation MCP server at https://handler.alduncanson.com/mcp or the page index at https://handler.alduncanson.com/llms.txt. See the agent skill guide.
1 maintainer
Metadata
1 maintainer
Release files for a2a-handler 0.3.0
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