📨 a2a-bus

A Reference Event Bus for Agent-to-Agent (A2A) Protocols

Because the ideas are:

🧠 Agents shouldn’t have to call each other directly.
📨 Let them speak in events.

a2a-bus is a schema-first, event-driven messaging architecture for intelligent agents that want to talk to each other — but without tight coupling or direct calls.

Instead of HTTP-based (direct) communication between agents, this repo demonstrates how to:

🧠 Publish and consume events over Kafka or NATS JetStream (w/ Docker Compose, but TODO)
📨 Standardize event structure using JSON Schema, Avro, and Protobuf
🔁 Simulate multi-agent flows with testing tools and local dev setups

🧪 Whether you're building tool-using LLM agents, multi-agent systems, or AI-native protocols — this repo is here to help you scale communication via topics, not endpoints.

✨ Why This Exists

Agent-to-agent (A2A) interoperability is emerging as a core challenge in the LLM and multi-agent ecosystem. Most current implementations are:

tightly coupled via REST/webhook calls,
hard to trace or replay,
lacking shared message schemas,
or too brittle to generalize.

This repo proposes a reference architecture using:

🧠 loosely coupled agents,
📨 brokered event flows,
📜 shared schema contracts, and
🔁 tooling to simulate, replay, and debug interactions.

Inspired by Google’s A2A protocol vision, but focused on real-world, event-driven backends.

📁 What’s Inside

a2a-bus/ ├── schema/ # 📜 JSON, Avro, and Proto3 message schemas
├── ts/ # 🧠 TypeScript agents (publisher, subscriber)
├── go/ # 🧠 Go-based agent implementations
├── python/ # 🧠 Python publisher/consumer samples
├── docker/ # 🐳 Kafka, Schema Registry, NATS JetStream
├── tools/ # 🔁 Simulator & testing CLI to publish A2A events
└── README.md # You are here.

🧪 Core Achievements

✅ Multi-language agents (TS, Go, Python) all speaking A2A
✅ Brokered communication over NATS using intent-based topics
✅ Schema-driven message formats (JSON Schema, Avro, Proto)
✅ CLI simulator agent for sending test messages and testing flows
✅ Docker Compose setup for local development and orchestration
✅ Standardized event format (headers, payload, meta) per A2A guidelines
✅ Message replay and test automation support (via test.sh)

🔧 Quickstart

# 1. Start all agents and brokers
docker compose up --build

# 2. Run a test message using the CLI simulator
./test.sh summarize.article "Hello from simulator"

Alternatively, invoke it manually:

docker compose run --rm simulator summarize.article "Hello from simulator"

Agents subscribed to the intent will receive the event and act on it.

🧰 Simulator CLI Tool

Located in tools/, the simulator can send any valid A2A event:

# Usage
docker compose run --rm simulator <intent> "<text>"

# Example
docker compose run --rm simulator summarize.article "Summarize this input text"

🧠 Use it to trigger agent flows, test message schemas, or script behaviors via test.sh.

🔑 Schema Notes

Please use schema/ definitions to ensure contract-based communication. Extend with your own tools, agents, or topics.

The schemas do not hardcode allowed values for intent, which is a deliberate and extensible choice. This allows agents to define new intents freely, including "summarize.article", "translate.snippet", "search.docs", etc.

🧑‍🤝‍🧑 Want to Contribute?

This project is early-stage, naive, and meant to inspire more robust agent bus standards. We welcome:

👀 feedback on schema design
💬 proposals for message types and routing
🔌 adapters for new brokers or runtimes
🧪 examples of agents in action

Open an issue or pull request — or just fork and experiment.

📜 License

Apache 2.0

hwclass / a2a-bus