strands.agent.a2a_agent

A2A Agent client for Strands Agents.

This module provides the A2AAgent class, which acts as a client wrapper for remote A2A agents, allowing them to be used standalone or as part of multi-agent patterns.

A2AAgent can be used to get the Agent Card and interact with the agent.

A2AAgent

class A2AAgent(AgentBase)

Defined in: src/strands/agent/a2a_agent.py:33

Client wrapper for remote A2A agents.

__init__

def __init__(endpoint: str,
             *,
             name: str | None = None,
             description: str | None = None,
             timeout: int = _DEFAULT_TIMEOUT,
             client_config: ClientConfig | None = None,
             a2a_client_factory: ClientFactory | None = None)

Defined in: src/strands/agent/a2a_agent.py:36

Initialize A2A agent.

Arguments:

• endpoint - The base URL of the remote A2A agent.
• name - Agent name. If not provided, will be populated from agent card.
• description - Agent description. If not provided, will be populated from agent card.
• timeout - Timeout for HTTP operations in seconds (defaults to 300).
• client_config - A2A ClientConfig for authentication and transport settings. The httpx_client configured here is used for both card discovery and message sending, enabling authenticated endpoints (SigV4, OAuth, bearer tokens). When providing an httpx_client, you are responsible for configuring its timeout.
• a2a_client_factory - Deprecated. Use client_config instead.

Raises:

• ValueError - If both client_config and a2a_client_factory are provided.

__call__

def __call__(prompt: AgentInput = None, **kwargs: Any) -> AgentResult

Defined in: src/strands/agent/a2a_agent.py:84

Synchronously invoke the remote A2A agent.

Arguments:

• prompt - Input to the agent (string, message list, or content blocks).
• **kwargs - Additional arguments (ignored).

Returns:

AgentResult containing the agent’s response.

Raises:

• ValueError - If prompt is None.
• RuntimeError - If no response received from agent.

invoke_async

async def invoke_async(prompt: AgentInput = None,
                       **kwargs: Any) -> AgentResult

Defined in: src/strands/agent/a2a_agent.py:104

Asynchronously invoke the remote A2A agent.

Arguments:

• prompt - Input to the agent (string, message list, or content blocks).
• **kwargs - Additional arguments (ignored).

Returns:

AgentResult containing the agent’s response.

Raises:

• ValueError - If prompt is None.
• RuntimeError - If no response received from agent.

stream_async

async def stream_async(prompt: AgentInput = None,
                       **kwargs: Any) -> AsyncIterator[Any]

Defined in: src/strands/agent/a2a_agent.py:132

Stream remote agent execution asynchronously.

This method provides an asynchronous interface for streaming A2A protocol events. Unlike Agent.stream_async() which yields text deltas and tool events, this method yields raw A2A protocol events wrapped in A2AStreamEvent dictionaries.

Arguments:

• prompt - Input to the agent (string, message list, or content blocks).
• **kwargs - Additional arguments (ignored).

Yields:

An async iterator that yields events. Each event is a dictionary:

• A2AStreamEvent: {“type”: “a2a_stream”, “event”: >A2A object>} where the A2A object can be a Message, or a tuple of (Task, TaskStatusUpdateEvent) or (Task, TaskArtifactUpdateEvent).
• AgentResultEvent: {“result”: AgentResult} - always emitted last.

Raises:

• ValueError - If prompt is None.

Example:

async for event in a2a_agent.stream_async("Hello"):
    if event.get("type") == "a2a_stream":
        print(f"A2A event: \{event['event']}")
    elif "result" in event:
        print(f"Final result: \{event['result'].message}")

get_agent_card

async def get_agent_card() -> AgentCard

Defined in: src/strands/agent/a2a_agent.py:182

Fetch and return the remote agent’s card.

Eagerly fetches the agent card from the remote endpoint, populating name and description if not already set. The card is cached after the first fetch.

When client_config is provided with an httpx_client, that client is used for card resolution, enabling authenticated card discovery (e.g., SigV4, OAuth, bearer tokens).

Returns:

The remote agent’s AgentCard containing name, description, capabilities, skills, etc.