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A2A Agent Delegation

CrewAI supports the Agent-to-Agent (A2A) protocol, allowing agents to delegate tasks to remote specialized agents. The agent’s LLM automatically decides whether to handle a task directly or delegate to an A2A agent based on the task requirements.
A2A delegation requires the a2a-sdk package. Install with: uv add 'crewai[a2a]' or pip install 'crewai[a2a]'

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How It Works

When an agent is configured with A2A capabilities:
  1. The LLM analyzes each task
  2. It decides to either:
    • Handle the task directly using its own capabilities
    • Delegate to a remote A2A agent for specialized handling
  3. If delegating, the agent communicates with the remote A2A agent through the protocol
  4. Results are returned to the CrewAI workflow

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Basic Configuration

Configure an agent for A2A delegation by setting the a2a parameter:
Code
from crewai import Agent, Crew, Task
from crewai.a2a import A2AConfig

agent = Agent(
    role="Research Coordinator",
    goal="Coordinate research tasks efficiently",
    backstory="Expert at delegating to specialized research agents",
    llm="gpt-4o",
    a2a=A2AConfig(
        endpoint="https://example.com/.well-known/agent-card.json",
        timeout=120,
        max_turns=10
    )
)

task = Task(
    description="Research the latest developments in quantum computing",
    expected_output="A comprehensive research report",
    agent=agent
)

crew = Crew(agents=[agent], tasks=[task], verbose=True)
result = crew.kickoff()

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Configuration Options

The A2AConfig class accepts the following parameters:
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endpoint
str
required
The A2A agent endpoint URL (typically points to .well-known/agent-card.json)
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auth
AuthScheme
default:"None"
Authentication scheme for the A2A agent. Supports Bearer tokens, OAuth2, API keys, and HTTP authentication.
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timeout
int
default:"120"
Request timeout in seconds
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max_turns
int
default:"10"
Maximum number of conversation turns with the A2A agent
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response_model
type[BaseModel]
default:"None"
Optional Pydantic model for requesting structured output from an A2A agent. A2A protocol does not enforce this, so an A2A agent does not need to honor this request.
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fail_fast
bool
default:"True"
Whether to raise an error immediately if agent connection fails. When False, the agent continues with available agents and informs the LLM about unavailable ones.

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Authentication

For A2A agents that require authentication, use one of the provided auth schemes:
  • Bearer Token
  • API Key
  • OAuth2
  • HTTP Basic
Code
from crewai.a2a import A2AConfig
from crewai.a2a.auth import BearerTokenAuth

agent = Agent(
role="Secure Coordinator",
goal="Coordinate tasks with secured agents",
backstory="Manages secure agent communications",
llm="gpt-4o",
a2a=A2AConfig(
    endpoint="https://secure-agent.example.com/.well-known/agent-card.json",
    auth=BearerTokenAuth(token="your-bearer-token"),
    timeout=120
)
)

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Multiple A2A Agents

Configure multiple A2A agents for delegation by passing a list:
Code
from crewai.a2a import A2AConfig
from crewai.a2a.auth import BearerTokenAuth

agent = Agent(
    role="Multi-Agent Coordinator",
    goal="Coordinate with multiple specialized agents",
    backstory="Expert at delegating to the right specialist",
    llm="gpt-4o",
    a2a=[
        A2AConfig(
            endpoint="https://research.example.com/.well-known/agent-card.json",
            timeout=120
        ),
        A2AConfig(
            endpoint="https://data.example.com/.well-known/agent-card.json",
            auth=BearerTokenAuth(token="data-token"),
            timeout=90
        )
    ]
)
The LLM will automatically choose which A2A agent to delegate to based on the task requirements.

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Error Handling

Control how agent connection failures are handled using the fail_fast parameter:
Code
from crewai.a2a import A2AConfig

# Fail immediately on connection errors (default)
agent = Agent(
    role="Research Coordinator",
    goal="Coordinate research tasks",
    backstory="Expert at delegation",
    llm="gpt-4o",
    a2a=A2AConfig(
        endpoint="https://research.example.com/.well-known/agent-card.json",
        fail_fast=True
    )
)

# Continue with available agents
agent = Agent(
    role="Multi-Agent Coordinator",
    goal="Coordinate with multiple agents",
    backstory="Expert at working with available resources",
    llm="gpt-4o",
    a2a=[
        A2AConfig(
            endpoint="https://primary.example.com/.well-known/agent-card.json",
            fail_fast=False
        ),
        A2AConfig(
            endpoint="https://backup.example.com/.well-known/agent-card.json",
            fail_fast=False
        )
    ]
)
When fail_fast=False:
  • If some agents fail, the LLM is informed which agents are unavailable and can delegate to working agents
  • If all agents fail, the LLM receives a notice about unavailable agents and handles the task directly
  • Connection errors are captured and included in the context for better decision-making

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Best Practices

Set Appropriate Timeouts

Configure timeouts based on expected A2A agent response times. Longer-running tasks may need higher timeout values.

Limit Conversation Turns

Use max_turns to prevent excessive back-and-forth. The agent will automatically conclude conversations before hitting the limit.

Use Resilient Error Handling

Set fail_fast=False for production environments with multiple agents to gracefully handle connection failures and maintain workflow continuity.

Secure Your Credentials

Store authentication tokens and credentials as environment variables, not in code.

Monitor Delegation Decisions

Use verbose mode to observe when the LLM chooses to delegate versus handle tasks directly.

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Supported Authentication Methods

  • Bearer Token - Simple token-based authentication
  • OAuth2 Client Credentials - OAuth2 flow for machine-to-machine communication
  • OAuth2 Authorization Code - OAuth2 flow requiring user authorization
  • API Key - Key-based authentication (header, query param, or cookie)
  • HTTP Basic - Username/password authentication
  • HTTP Digest - Digest authentication (requires httpx-auth package)

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Learn More

For more information about the A2A protocol and reference implementations: