a2acli

a2acli — A2A Protocol CLI

a2acli is a command-line tool for interacting with agents that expose the A2A (Agent-to-Agent) protocol. It supports both standard HTTP transports (JSON-RPC, REST) and SLIM RPC for agents deployed behind a SLIM messaging node.

Setup

1. Build the binary

From the skill directory:

# Build and place in this skill's scripts/ directory
task build-skill

# Or install to your PATH
task install

2. Add AgentCard files

AgentCard JSON files must be placed in a .a2aagents directory. The CLI searches:

1. .a2aagents/ in the current working directory
2. ~/.a2aagents/ in the home directory

You can override this with --agents-dir <path>.

Each agent is identified by the SHA256 digest of its AgentCard JSON file (e.g. sha256:3f7a2c1b...). You can use the full digest or any unambiguous prefix.

---

Commands

scripts/a2acli list

List all available agents.

scripts/a2acli list [--agents-dir <path>]

Output:

NAME                  DESCRIPTION                                       DIGEST
weather-agent         Provides weather forecasts for any location        sha256:3f7a2c1b...
code-review-agent     Reviews Go, Python and TypeScript code             sha256:9d4e8f2a...

---

scripts/a2acli get-card --agent <digest>

Print the full AgentCard JSON for an agent, including all skills, capabilities, and supported interfaces.

scripts/a2acli get-card --agent <digest>

Example:

scripts/a2acli get-card --agent sha256:3f7a2c1b

Output: Pretty-printed AgentCard JSON, for example:

{
  "name": "weather-agent",
  "description": "Provides weather forecasts for any location",
  "version": "1.0",
  "skills": [
    {
      "id": "get-forecast",
      "name": "Get Forecast",
      "description": "Returns a weather forecast for a given location and date range",
      "tags": ["weather", "forecast"]
    }
  ],
  "capabilities": {
    "streaming": false
  },
  ...
}

Use this command when you need to understand what an agent can do before sending it a message.

---

scripts/a2acli send-message --agent <digest> [--return-immediately] "<message>"

Send a text message to an agent.

scripts/a2acli send-message --agent <digest> [--return-immediately] "<message>"

Flags:

• --return-immediately — Instruct the agent to return a Task immediately without waiting for completion. The Task ID and initial status are printed; no polling is performed. Without this flag the CLI polls every 2 seconds until the task reaches a terminal state.

Example — synchronous response (agent replies with a Message):

$ scripts/a2acli send-message --agent sha256:3f7a2c1b "What is the weather in London tomorrow?"
The forecast for London tomorrow is partly cloudy with a high of 18°C and a low of 11°C.

Example — async response, poll until done (default):

$ scripts/a2acli send-message --agent sha256:9d4e8f2a "Review the code in main.go for security issues"
Task ID: 01938f4a-1234-7abc-def0-123456789abc
Waiting for task to complete...
Status: TASK_STATE_WORKING
Status: TASK_STATE_COMPLETED

Final status: TASK_STATE_COMPLETED

Artifact 1: code-review
Found 2 potential issues:
1. SQL query on line 42 uses string concatenation — use parameterized queries instead.
2. Error from os.ReadFile on line 67 is silently ignored.

Example — return immediately, retrieve result later:

$ scripts/a2acli send-message --agent sha256:9d4e8f2a --return-immediately "Generate a report"
Task ID: 01938f4a-1234-7abc-def0-123456789abc
Status:  TASK_STATE_SUBMITTED

---

scripts/a2acli get-task --agent <digest> "<task-id>"

Retrieve the current state of a task, including its status, history, and any artifacts.

scripts/a2acli get-task --agent <digest> "<task-id>"

Example:

$ scripts/a2acli get-task --agent sha256:9d4e8f2a "01938f4a-1234-7abc-def0-123456789abc"

Output: The full task as JSON:

{
  "id": "01938f4a-1234-7abc-def0-123456789abc",
  "contextId": "01938f49-5678-7abc-def0-abcdef012345",
  "status": {
    "state": "TASK_STATE_COMPLETED"
  },
  "artifacts": [
    {
      "artifactId": "01938f4b-...",
      "name": "code-review",
      "parts": [
        {
          "text": "Found 2 potential issues:\n1. ..."
        }
      ]
    }
  ]
}

---

Global Flags

---

Common Workflows

Discover and query an agent

# 1. List available agents to find the one you need
scripts/a2acli list

# 2. Inspect its capabilities and skills
scripts/a2acli get-card --agent sha256:3f7a2c1b

# 3. Send a message and wait for the result
scripts/a2acli send-message --agent sha256:3f7a2c1b "Hello, what can you do?"

Fire-and-forget a long-running task

# Submit the task and get the ID immediately
scripts/a2acli send-message --agent sha256:9d4e8f2a --return-immediately "Analyze the sales data for Q1 2025"
# Task ID: 01938f4a-1234-7abc-def0-123456789abc
# Status:  TASK_STATE_SUBMITTED

# Check back later
scripts/a2acli get-task --agent sha256:9d4e8f2a "01938f4a-1234-7abc-def0-123456789abc"

Use a non-default agents directory

scripts/a2acli --agents-dir /path/to/my/agents list
scripts/a2acli --agents-dir /path/to/my/agents send-message --agent sha256:3f7a2c1b "Hello"

---

Task States