Overview

Relevant source files

Purpose and Scope

This document provides a comprehensive introduction to the Agent2Agent (A2A) Protocol project, covering its mission to enable standardized communication between AI agents, core architectural components, and key value propositions. This overview establishes the foundation for understanding A2A's role in the agentic AI ecosystem.

For detailed protocol specifications, see Protocol Specification. For implementation guidance, see SDK Documentation. For community and governance information, see Community & Development.

What is A2A Protocol

The Agent2Agent (A2A) Protocol is an open standard that enables seamless communication and collaboration between AI agents built on diverse frameworks and deployed by different vendors. A2A addresses the critical challenge of agent interoperability by providing a common communication language that allows agents to discover each other's capabilities, negotiate interaction modalities, and collaborate on complex tasks while maintaining operational opacity.

A2A operates as a universal protocol layer that sits between agentic applications, similar to how HTTP enables web communication. It supports multiple transport mechanisms including JSON-RPC 2.0 over HTTP(S), gRPC over HTTP/2, and REST-style HTTP+JSON, providing flexibility for different deployment scenarios.

Core A2A System Architecture

Sources: README.md1-86 docs/index.md14-125

Core Protocol Components

A2A is built around five fundamental data structures that enable agent discovery, task management, and rich communication. These components are formally defined in the JSON schema and TypeScript type definitions.

A2A Protocol Component Mapping

Sources: README.md20-26 README.md42-46

The protocol centers around these key entities:

Entity	Purpose	Key Properties
`AgentCard`	Agent discovery and capability advertisement	`capabilities[]`, `supportedTransports`, `authenticationSchemes`
`Task`	Stateful work units with lifecycle management	`taskId`, `status`, `messages[]`, `artifacts[]`
`Message`	Communication within tasks	`messageId`, `parts[]`, `sender`, `timestamp`
`Part`	Content containers supporting multiple media types	`type`, `content`, `mimeType`
`Artifact`	Persistent task outputs	`artifactId`, `metadata`, `content`

Key Value Propositions

A2A delivers four primary value propositions that address critical challenges in the agentic AI landscape:

Interoperability Across Frameworks

A2A enables agents built on different platforms (LangGraph, CrewAI, Semantic Kernel, custom solutions) to communicate seamlessly. This breaks down technology silos and allows organizations to leverage best-of-breed agent solutions without vendor lock-in.

Complex Multi-Agent Workflows

The protocol supports sophisticated collaboration patterns where specialized agents can delegate sub-tasks, exchange information, and coordinate actions to solve problems beyond the capability of any single agent.

Security Through Opacity

Agents interact without needing to share internal memory, tools, or proprietary logic. This preserves intellectual property and enhances security by maintaining operational boundaries between agent systems.

Enterprise-Ready Architecture

A2A includes built-in support for authentication schemes, observability, and production deployment patterns required for enterprise adoption.

Sources: docs/index.md96-110 README.md32-47

Ecosystem Position

A2A complements other protocols and frameworks in the AI agent ecosystem rather than competing with them. The protocol operates at the agent-to-agent communication layer, while other standards handle different concerns.

A2A Ecosystem Integration

Sources: docs/index.md119-124 README.md53-57

Key ecosystem relationships:

Model Context Protocol (MCP): Handles agent-to-tool communication within individual agents
Agent Development Kit (ADK): Google's framework for building A2A-compliant agents
LangGraph/CrewAI/Semantic Kernel: Agent frameworks that can integrate A2A for inter-agent communication
Framework Integrations: Built-in A2A support in BeeAI Framework, Pydantic AI, and other platforms

Project Governance and Community

The A2A Protocol operates under open-source governance with backing from major technology companies and active community contribution. The project is licensed under Apache 2.0 and maintained through a structured contribution process.

The protocol specification is maintained in the main repository with automated schema generation from TypeScript definitions to ensure consistency across language implementations. Multiple SDK repositories provide language-specific implementations while maintaining protocol compatibility.

Sources: README.md59-68 README.md84-86 docs/community.md1-88