a2a-cli

A command-line interface for the Agent-to-Agent (A2A) protocol v0.3.
Send messages, stream responses, inspect agent cards, and manage tasks — from your terminal, against any A2A-compatible server.

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Install

pip install a2a-cli

Requirements: Python 3.10+

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Quick start

# List all agents on a server
a2a list --agent http://localhost:8080/a2a

# Inspect an agent
a2a card --agent http://localhost:8080/a2a/my-agent

# Send a message
a2a send "What is the capital of France?" --agent http://localhost:8080/a2a/my-agent

# Stream the response live (SSE)
a2a stream "Summarize this for me" --agent http://localhost:8080/a2a/my-agent

# Check a task
a2a get <task-id> --agent http://localhost:8080/a2a/my-agent

# Cancel a running task
a2a cancel <task-id> --agent http://localhost:8080/a2a/my-agent

Set A2A_AGENT so you don't repeat --agent every time:

export A2A_AGENT=http://localhost:8080/a2a/my-agent
a2a send "hello"
a2a card

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Commands

a2a list

List all agents exposed by an A2A server.

a2a list --agent http://localhost:8080/a2a

                        Exposed Agents
┏━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Name                ┃ URL                                      ┃
┡━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ greeter             │ http://localhost:8080/a2a/greeter         │
│ support_agent       │ http://localhost:8080/a2a/support_agent   │
│ weather_reporter    │ http://localhost:8080/a2a/weather_reporter│
└─────────────────────┴──────────────────────────────────────────┘

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a2a card

Fetch and display the agent card (/.well-known/agent-card.json).

a2a card --agent http://localhost:8080/a2a/greeter

╭──────────────────────── Agent Card ────────────────────────╮
│ greeter                                                     │
│ Version:     1                                              │
│ URL:         http://localhost:8080/a2a/greeter              │
│ Description: Agent workflow for greeter                     │
│                                                             │
│ Skills:                                                     │
│   • greeter  Agent workflow for greeter                     │
╰─────────────────────────────────────────────────────────────╯

Use --json for the raw agent card JSON:

a2a card --agent http://localhost:8080/a2a/greeter --json

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a2a send

Send a message and display the result.

a2a send "hello world" --agent http://localhost:8080/a2a/my-agent

╭──────────────────────── A2A Task ──────────────────────────╮
│ Task ID: dcc14eac-364d-42e3-95f3-69f2c2b0f47c              │
│ State:   completed                                          │
│                                                             │
│ Output:                                                     │
│   Hello! You said: hello world                              │
╰─────────────────────────────────────────────────────────────╯

Options:

Flag	Description
--json	Print raw JSON response
--quiet, -q	Print only the response text (great for scripting)
--context-id	Conversation context ID for multi-turn exchanges
--task-id	Continue an existing task

# Scripting — just the output text
a2a send "hello" --agent http://localhost:8080/a2a/my-agent --quiet

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a2a stream

Send a message and stream the response live via SSE.

a2a stream "Write a summary" --agent http://localhost:8080/a2a/my-agent

● working
● completed
  Here is the summary...

Use --json to print raw SSE events:

a2a stream "hello" --agent http://localhost:8080/a2a/my-agent --json

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a2a get

Fetch the current state of a task by ID.

a2a get dcc14eac-364d-42e3-95f3-69f2c2b0f47c --agent http://localhost:8080/a2a/my-agent

╭──────────────────────── A2A Task ──────────────────────────╮
│ Task ID: dcc14eac-364d-42e3-95f3-69f2c2b0f47c              │
│ State:   completed                                          │
│                                                             │
│ Output:                                                     │
│   Hello! You said: hello world                              │
╰─────────────────────────────────────────────────────────────╯

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a2a cancel

Cancel a running task.

a2a cancel dcc14eac-364d-42e3-95f3-69f2c2b0f47c --agent http://localhost:8080/a2a/my-agent

Canceled task dcc14eac-364d-42e3-95f3-69f2c2b0f47c

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Global options

Flag	Description
--agent, -a	Agent URL. Falls back to A2A_AGENT env var
--header, -H	Extra request header, repeatable: "Authorization: Bearer <token>"

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Protocol

Implements A2A v0.3:

• message/send — synchronous request/response
• message/stream — streaming via SSE
• tasks/get — task status and output
• tasks/cancel — cancel a running task
• Agent card discovery at /.well-known/agent-card.json

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Tested with

• Conductor A2A server

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License

Apache 2.0 — conductor-oss/a2a-cli