A2A Design Principles

Table of Contents

1. Introduction: Why A2A Matters in the Age of Autonomous Agents
2. Design Principles Overview
3. A2APrinciple 1: Embrace Agentic Capabilities
4. A2APrinciple 2: Build on Existing Standards
5. A2APrinciple 3: Secure by Default
6. A2APrinciple 4: Support for Long-Running Tasks
7. A2APrinciple 5: Modality Agnostic
8. Conclusion: Designing for the Agent Ecosystem Ahead

Introduction: Why A2A Matters in the Age of Autonomous Agents

Lately, AI agents have been increasing exponentially. Their demand is at its peak. This triggers the need for a standard. Just like the internet needed HTTP and microservices needed REST/gRPC, agents now need a shared protocol for working together.

Enter A2A (agent-to-agent) — an open protocol announced by Google, designed to enable agents to collaborate safely and reliably, regardless of their design or purpose.

In this article, we will break down the five core design principles of A2A using real-world analogies, simple architectural takeaways, and practical tips. Whether you're designing a single-purpose agent or building a full agent network, understanding these principles will help you build systems that are scalable, secure, and future-proof.

Design Principles Overview

We will venture into the 5 core design principles of A2A (Agent-to-Agent). They provide a foundation for building scalable, secure, and interoperable agent-based systems. Here’s a quick overview of each:

1. Embrace Agentic Capabilities: Understand how A2A enables agents to operate autonomously, without relying on shared memory or tools.
2. Build on Existing Standards: Explore how A2A leverages existing, widely accepted standards to simplify integration.
3. Secure by Default: Learn how A2A integrates strong authentication and authorization mechanisms into communication.
4. Support for Long-Running Tasks: Learn how A2A plans to handle long-running tasks using event streaming.
5. Modality Agnostic: See how A2A supports a variety of input/output modalities (text, voice, images, etc.), ensuring that agents can communicate regardless of which modalities they use.

A2APrinciple 1: Embrace Agentic Capabilities

Official Definition

A2A focuses on enabling agents to collaborate in their natural, unstructured modalities, even when they don’t share memory, tools, or context. We are enabling true multi-agent scenarios without limiting an agent to a “tool.”

Developer-Friendly Explanation

Each agent should function like a standalone service. It shouldn't assume access to a shared database, memory, or other tools. Each one just needs to know how to communicate with the others, not what’s inside them.

Analogy: Zero-Trust Microservices

Consider backend services working in a secure system. They operate under the following conditions:

• They don’t share memory.
• They only communicate through defined APIs.
• They don’t trust each other by default.

Each service focuses on its job, and that’s exactly what A2A wants for agents.

Architectural Implications

• Agents can reside on different machines, written in different languages.
• No shared memory = easier scaling and problem isolation.
• Agents must communicate using clear protocols rather than internal state.
• This promotes loose coupling—a common best practice in system design.

Design Tips or Pitfalls

Do:

• Give each agent a clear role and a clean interface.
• Each agent should assume it knows nothing about other agents' interfaces.

Don’t:

• Assume agents can see or share memory/tools.
• Hardcode links between agents.

Future-Facing Note

This principle makes it easier to build agent networks where:

• Agents come from different teams or vendors.
• Agents can be replaced or upgraded independently.
• Agents collaborate on long, multi-step tasks.

It sets the stage for true multi-agent systems that scale like microservices.

A2APrinciple 2: Build on Existing Standards

The protocol is built on top of existing, popular standards including HTTP, SSE, and JSON-RPC, which means it’s easier to integrate with existing IT stacks that businesses already use daily.

Developer-Friendly Explanation

Instead of creating new protocols, A2A is built on top of well-known standards. This means you can use familiar tools and libraries to make agents communicate. For example, you can use HTTP to make requests, JSON-RPC for structured messages, and more. It makes integration easy for developers.

Analogy: Building with Lego Blocks

Imagine building a Lego model with a huge collection of Lego pieces you already have. Instead of creating custom pieces, you use what’s already in the box. This is how A2A works—it utilizes established tools to build robust systems without reinventing the wheel.

Architectural Implications

• Familiarity: Developers don’t need to learn new tech stacks.
• Extensibility: Since A2A uses open standards, it’s easy to add new functionality.
• Interoperability: Systems that already use HTTP or JSON-RPC can easily plug into A2A.

Design Tips or Pitfalls

Do:

• Use standard HTTP status codes and REST conventions to ensure easy integration.
• Use JSON schema to define interfaces for communication.

Don’t:

• Overcomplicate the communication protocol.
• Assume that complex proprietary protocols will improve interoperability.

Future-Facing Notes

By using established protocols, A2A positions itself to easily integrate with future technologies.

A2APrinciple 3: Secure by Default

A2A is designed to support enterprise-grade authentication and authorization, with parity to OpenAPI’s authentication schemes at launch.

Developer-Friendly Explanation

A2A makes security a priority from the start. This means that every agent interaction is protected by strong security mechanisms. Rather than adding security as an afterthought, A2A embeds it into the design.

Analogy: Bank Vaults

Think of agent communication like using a secure bank vault:

• Before anything can happen, agents must authenticate with proper credentials.
• Only authorized agents can access certain vaults.
• All interactions are encrypted.

This ensures only trusted agents can communicate—and that their communication is secure and private.

Architectural Implications

• Mandatory security layer: A2A integrates features like OAuth and JWT to authenticate agents. This means security is the default, not an option.
• Data protection: Secure communication must happen over encrypted channels.
• Granular access control: Using ACLs, A2A can define exactly what agents are allowed to do.

Design Tips or Pitfalls

Do:

• Leverage OAuth or JWT.
• Implement RBAC to specify what each agent can or cannot do.

Don’t:

• Skip security during early development.
• Assume that local deployments are safe—always use encryption for agent interactions.

Future-Facing Note

A2A’s security-first design ensures that as agent ecosystems grow, security stays intact. As agents evolve, more advanced security can be integrated seamlessly.

A2APrinciple 4: Support for Long-Running Tasks

We designed A2A to be flexible and support scenarios where it excels at completing everything—from quick tasks to deep research that may take hours or even days when humans are in the loop. Throughout this process, A2A can provide real-time feedback, notifications, and state updates to its users.

Developer-Friendly Explanation

Not all tasks are instant. Some might take hours or days.

A2A handles this by letting agents:

• Start a task
• Send progress updates while it’s running
• Notify when it’s finished or if something went wrong

You don’t need to block or poll—A2A provides an event stream for updates using Server-Sent Events (SSE).

Analogy: Food Delivery Tracker

It’s like ordering food with a delivery app:

• You place the order (task request)
• You see updates like "order confirmed", "preparing", "out for delivery"
• You get a final "delivered" or "failed" notification

A2A treats agent tasks the same way—keeping the calling agent informed without needing to constantly check.

Architectural Implications

• Asynchronous workflows become easy to manage
• Agents can run independently and still coordinate over time
• Events can be used to chain tasks, notify users, or trigger other agents

Design Tips or Pitfalls

Do:

• Use SSE for streaming task updates to subscribers
• Model tasks with unique IDs and predictable lifecycle states
• Handle retries and fallbacks when needed

Don’t:

• Assume agents will return results instantly
• Block on long tasks

Future-Facing Note

As agents start performing multi-step or AI-powered tasks, long-running operations must occur. A2A’s support for streaming updates ensures that these complex operations remain observable and controllable.

A2APrinciple 5: Modality Agnostic

The agentic world isn’t limited to just text, which is why we’ve designed A2A to support various modalities, including audio and video streaming.

Developer-Friendly Explanation

Agents should be able to work in any format. One agent might understand images, another code, another voice. A2A doesn’t care how agents communicate, as long as they follow the rules for structured messaging.

Analogy: USB Port for Agents

Think of A2A like a USB agent port.

You can plug in a mouse, keyboard, printer, or phone—but they all work because they follow a shared protocol.

Same with A2A agents: voice agents, vision agents, text agents, and action agents all connect as long as they speak the same protocol.

Architectural Implications

• You can build multimodal systems.
• It supports specialized agents working in harmony.
• You aren’t locked into a single modality. This makes your system more future-proof.

Design Tips or Pitfalls

Do:

• Clearly define what modality your agent accepts/returns.
• Use structured metadata to describe messages.

Don’t:

• Hardcode assumptions about input/output formats.
• Build tightly coupled agents that expect specific tools or formats.

Future-Facing Note

Modality-agnostic design sets the stage for true multimodal AI systems. Agents will be able to evolve without breaking interoperability.

Conclusion: Designing for the Agent Ecosystem Ahead

A2A is more than just a messaging protocol. It's like a philosophy for creating autonomous systems that are modular, interoperable, and secure by default.

By:

• Treating agents as standalone peers
• Building on open standards
• Enforcing strong security
• Supporting asynchronous, long-running workflows
• And staying modality agnostic

...A2A lays the foundation for future agents.

As developers, we now have a specification we can follow to create better agents. Happy developing!

Frequently Asked Questions