A2A Protocol

A2A Protocol is an open standard for AI agents from different frameworks and vendors to talk to each other.

The Agent2Agent (A2A) Protocol is an open standard for communication between opaque agentic applications. Agents built with ADK, LangGraph, CrewAI, Semantic Kernel or custom code can delegate tasks, exchange information and coordinate, without sharing memory, tools or proprietary logic. Formal extensions add capabilities while the core stays stable. Official SDKs cover Python, JavaScript, Java, C#/.NET, Go and Rust, and an a2a-cli can discover and message agents from a terminal. The project has joined the Agentic AI Foundation. Tutorials, the specification and sample clients and servers are on the site and GitHub.

A2A Protocol at a glance

Best for: Software engineer
Runs on: open source
Pricing: Free and open source
Released: March 2025
Category: AI agent tool
Website: a2a-protocol.org

Key features

Open protocol for agent-to-agent messages
Works across LangGraph, CrewAI, Semantic Kernel and custom agents
Opaque: no need to share memory, tools or internals
Official SDKs for Python, JS, Java, .NET, Go and Rust
a2a-cli to discover and message agents
Extension process so the core protocol stays stable

Use it for

Let a research agent hand a sub-task to a coding agent
Expose an in-house agent to partners without opening its tools
Drive any A2A agent from a terminal during development

Alternatives to A2A Protocol

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Agenta — Build and automate AI agents that run on your own infrastructure or the cloud.
Agent Delegated Authority — It defines cryptographically verifiable authorization receipts and deterministic boundaries.
World2Agent — Standardizes how AI agents perceive real-world events.
Aroha Protocol — Enforce cryptographic control and spending caps across agent chains.
OpenAI Agents SDK JS — Builds multi-agent workflows and voice agents with native handoffs.
Agent2api — It combines multiple AI desktop client accounts into one local OpenAI-compatible API.
Adyen — Share AI agent resources across coding tools and repositories easily.
OpenAI Agents SDK — Provider-agnostic multi-agent framework with built-in guardrails and tracing.
II-Agent — It provides a fully open-source, transparent, and auditable agent foundation.
Composio — Equips AI agents with tools, managed user auth, and sandboxes across 1,500+ apps

All A2A Protocol alternatives