Key Principles of A2A Protocol

The Agent2Agent Protocol (A2A) is designed with several fundamental principles to ensure effective and secure communication between autonomous AI agents. These principles guide its architecture and implementation.

Opaque Agent Design

A2A treats agents as opaque systems, meaning:

• Agents don't share their internal memory, tools, or resources
• Each agent maintains its own autonomy and encapsulation
• Communication happens through well-defined interfaces, not by exposing internals
• Agents don't need to know how other agents work internally

This design enables agents from different vendors and using different frameworks to interact without needing to understand each other's implementation details.

Enterprise Readiness

A2A is designed with enterprise requirements in mind:

• Security: Strong authentication and authorization using standard protocols
• Compliance: Designed to work within enterprise security models
• Scalability: Support for both simple and complex integration scenarios
• Reliability: Well-defined error handling and status reporting
• Auditability: Task history and state transitions can be tracked

Task-Oriented Communication

All A2A communication is centered around tasks:

• Tasks represent units of work requested by a client from an agent
• Tasks have clear states (submitted, working, input-required, completed, etc.)
• Tasks can be tracked, monitored, and canceled
• Task results are delivered as structured artifacts

This task-oriented approach provides clear boundaries and expectations for both clients and agents.

Flexible Content Exchange

A2A supports multiple types of content:

• Plain text communication
• Structured data (JSON)
• Files and binary data
• Multi-part messages
• Streaming responses

This flexibility allows agents to communicate in the most appropriate format for the task at hand.

Standard Protocols

A2A builds on established standards:

• HTTP as the transport layer
• JSON-RPC 2.0 for message formatting
• Server-Sent Events (SSE) for streaming
• OpenAPI authentication patterns

Using these standards ensures compatibility with existing systems and tools.

Agent Capability Discovery

A2A includes a mechanism for agents to advertise their capabilities:

• Agents publish an Agent Card describing their skills and requirements
• Clients can discover and select the most appropriate agent for a task
• Skills are described with human-readable names, descriptions, and examples
• Agents specify their supported input and output formats

This discovery mechanism allows for dynamic, flexible agent ecosystems.

Asynchronous and Stateful Interaction

A2A supports both synchronous and asynchronous communication:

• Clients can receive immediate responses for simple tasks
• Long-running tasks can be monitored through polling or notifications
• Push notifications can update clients about task status changes
• Multi-turn conversations allow for complex, interactive tasks

These principles together create a protocol that enables robust, secure, and flexible communication between autonomous agents in enterprise environments.