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The skill and the binary can always be installed independently — the plugin is a convenience, never a precondition. + +## Contents + +```text +agent-plugin/ +├── plugin.json # manifest (Agent Plugins 1.0.0) +├── LICENSE # Apache-2.0 +└── skills/ + └── a2a-cli/ + └── SKILL.md # agent-facing usage guidance +``` + +Skills-only: this plugin carries no MCP server, which is valid under Agent Plugins (a skills-only plugin conforms). + +## Requires the `a2a` binary + +Agent Plugins packages the agent-facing pieces (skills and MCP servers), not tool binaries. The `a2a` binary is **not** bundled and must be installed separately (Homebrew, WinGet, a prebuilt release, or `go install`) — see the [project README](https://github.com/a2aproject/a2a-cli#installation) and the skill's own Setup section. The skill includes a preflight check (`a2a version`). + +## Install + +With the [`skills`](https://github.com/vercel-labs/skills) CLI, from this repository: + +```bash +# from a local checkout +npx skills add ./agent-plugin/skills/a2a-cli -g + +# or directly from GitHub +npx skills add https://github.com/a2aproject/a2a-cli/tree/main/agent-plugin/skills/a2a-cli -g +``` + +A plugin-aware client can instead load this directory as an Agent Plugin: it reads `plugin.json`, discovers skills under `skills/`, and validates each `SKILL.md`. Installation, enablement, and updates are client-controlled. + +## Versioning + +The plugin `version` in `plugin.json` (`0.2.0`) tracks the `a2a` CLI release; the bundled skill keeps its own date-based `metadata.version`. The manifest targets Agent Plugins spec **1.0.0**. diff --git a/agent-plugin/plugin.json b/agent-plugin/plugin.json new file mode 100644 index 0000000..014ad48 --- /dev/null +++ b/agent-plugin/plugin.json @@ -0,0 +1,14 @@ +{ + "$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json", + "name": "a2a-cli", + "version": "0.2.0", + "description": "Drive A2A (Agent2Agent) agents from the command line with the a2a CLI: fetch an agent card, send a message, stream or poll a task, and list, resume, or cancel tasks.", + "author": { + "name": "A2A Project", + "url": "https://a2a-protocol.org" + }, + "homepage": "https://github.com/a2aproject/a2a-cli", + "repository": "https://github.com/a2aproject/a2a-cli", + "license": "Apache-2.0", + "keywords": ["a2a", "agent2agent", "cli", "agents", "interoperability", "agent-card"] +} diff --git a/agent-plugin/skills/a2a-cli/SKILL.md b/agent-plugin/skills/a2a-cli/SKILL.md new file mode 100644 index 0000000..ef5ae13 --- /dev/null +++ b/agent-plugin/skills/a2a-cli/SKILL.md @@ -0,0 +1,134 @@ +--- +name: a2a-cli +description: >- + Delegate work to A2A (Agent2Agent) agents from the command line with the `a2a` + CLI (github.com/a2aproject/a2a-cli). Use when you need to hand a task to a + specialized or remote agent, fetch an agent's card, send a message to an agent + at a URL, stream or poll a running task, or check, list, resume, or cancel an + A2A task. Not for building or serving an A2A agent, or for calling non-A2A + HTTP APIs. +compatibility: >- + Requires the `a2a` binary on PATH. Install it with Homebrew or WinGet, from a + prebuilt release binary, or from source with a Go toolchain. The skill installs + nothing itself. +license: Apache-2.0 +metadata: + source: https://github.com/a2aproject/a2a-cli + version: "2026.09.08" +--- + +# Driving A2A agents with the `a2a` CLI + +`a2a` is a stateless client for the [A2A protocol](https://a2a-protocol.org/): +give it an agent and a message, it negotiates the transport from the agent's +card (JSON-RPC, REST, or gRPC), sends the message, and reports what the agent +returned. + +## Core concepts + +- An interaction starts with a **Message** you send to an agent. +- The agent replies with either a **Message** (a direct answer) or a **Task** + (tracked, potentially long-running work). +- A **Task** has a server-assigned `taskId` and a `contextId`, and moves through + states. It can complete, fail, be cancelled, or become **interrupted** when it + needs your input or authentication to continue. +- Resume an interrupted task by sending a Message with its `--task-id`. +- Group related work with `--context-id`: a Task created in reply joins that + context. Many tasks can share one context, and a `--task-id` and `--context-id` + passed together must agree. +- The server keeps tasks (and the messages tied to them); a plain Message not + tied to a task is not stored — so **you** hold the `taskId`/`contextId` to + return to work later. + +## Setup + +The skill needs the `a2a` binary on PATH — check with `a2a version`. If it is +missing, install it with Homebrew (`brew tap a2aproject/a2a-cli +https://github.com/a2aproject/a2a-cli && brew install a2a`), WinGet +(`winget install a2aproject.a2acli`), a prebuilt binary from the +[releases page](https://github.com/a2aproject/a2a-cli/releases/latest), or from +source with a Go toolchain (re-run to update): + +```bash +go install github.com/a2aproject/a2a-cli@latest + +# rename to a2a to match the docs + +mv "$(command -v a2a-cli)" "$(dirname "$(command -v a2a-cli)")/a2a" +``` + +The tool is under active development. Treat `a2a help` and `a2a +--help` as the source of truth for the current commands and flags. + +## Task lifecycle + +Point at an agent with `-a ` (resolves its card and picks a +transport) or `-e --transport ` (connect directly). + +1. **Inspect the agent** — confirm it is reachable and see what it supports: + + ```bash + a2a card get https://agent.example.com + ``` + +2. **Send a message.** `send` blocks until the task reaches a terminal or + interrupted state. Add `-o json` for machine-readable output, and note the + `taskId` and `contextId` in the response — you need them to continue: + + ```bash + a2a send -a https://agent.example.com "Summarize this repo" + a2a send -a https://agent.example.com -o json "Summarize this repo" + ``` + +3. **Follow a long task live** instead of blocking, or re-attach to one later: + + ```bash + a2a send -a https://agent.example.com --stream "Run a long analysis" + a2a task subscribe -a https://agent.example.com + ``` + +4. **Check status and fetch results** at any time: + + ```bash + a2a task get -a https://agent.example.com + ``` + +5. **Answer an interrupted task** (it reached `INPUT_REQUIRED` / `AUTH_REQUIRED`) + by replying on the same task: + + ```bash + a2a send -a https://agent.example.com --task-id "Yes, proceed" + ``` + +6. **Continue the conversation** as a new task in the same context: + + ```bash + a2a send -a https://agent.example.com --context-id "Follow-up question" + ``` + +7. **List or cancel tasks:** + + ```bash + a2a task list -a https://agent.example.com + a2a task cancel -a https://agent.example.com + ``` + +## Key flags + +Run `a2a --help` for the full, current set. The load-bearing ones: + +| Flag | Use | +|---|---| +| `-a, --agent-card ` | Resolve the agent's card (picks the transport). | +| `-e, --endpoint ` + `--transport ` | Connect to one interface directly, skipping card resolution. | +| `-o, --output json` | Machine-readable output; add `--stream` for a live event stream. | +| `--async` | Return immediately with the identifiers instead of blocking; poll later with `task get`. | +| `--task-id ` / `--context-id ` | Continue a task / group a new task under a context. | +| `--auth ""` / `--svc-param ` | Attach credentials or transport parameters (or set `A2ACLI_*` env vars). Never commit a secret. | + +## Configuration + +Every setting can come from a flag, an `A2ACLI_*` environment variable, or a +`.env` file (a local `.env`, or `~/.config/a2a-cli/.env`); precedence is +flag > env var > file. Inspect the effective values and where each resolved from +with `a2a config show` (secrets redacted).