Server: A2A

Deploy agents as A2A (Agent-to-Agent) protocol servers

Deploy agents as A2A servers for agent-to-agent communication.

CLI

pip install "praisonaiagents[os]"
export OPENAI_API_KEY="your-key"

# Start A2A server
praisonai serve a2a --port 8001

Option	Default	Description
--host	127.0.0.1	Host to bind to
--port	8001	Server port
--file	agents.yaml	Agents YAML file

Python

from praisonaiagents import Agent, A2A

agent = Agent(
    name="Assistant",
    role="Helpful AI Assistant",
    goal="Help users with their questions",
    llm="gpt-4o-mini"
)

a2a = A2A(agent=agent)
a2a.serve(host="0.0.0.0", port=8000)

serve() creates a FastAPI app and starts uvicorn for you. For custom FastAPI apps, use a2a.get_router() instead.

Expected Output:

INFO:     Started server process
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000

Verify:

curl http://localhost:8000/.well-known/agent.json

Response:

{
  "name": "Assistant",
  "description": "Helpful AI Assistant",
  "url": "http://localhost:8000/a2a",
  "version": "1.0.0",
  "capabilities": {
    "streaming": true,
    "pushNotifications": false,
    "stateTransitionHistory": false
  }
}

agents.yaml

A2A server is Python-only. No agents.yaml support.

A2A Endpoints

Endpoint	Method	Description
/.well-known/agent.json	GET	Agent Card for discovery
/a2a	POST	JSON-RPC messages
/status	GET	Server status

A2A Parameters

Parameter	Type	Default	Description
agent	Agent	—	PraisonAI Agent instance
agents	AgentTeam	—	Multi-agent team (agents.start() is called)
name	str	agent.name	A2A endpoint name
description	str	agent.role	Agent description
url	str	http://localhost:8000/a2a	A2A endpoint URL
version	str	1.0.0	Version string
prefix	str	""	URL prefix
auth_token	str	None	Bearer token for POST /a2a auth

Authentication

a2a = A2A(agent=agent, auth_token="sk-my-secret-key")
a2a.serve(port=8000)

Clients must send Authorization: Bearer sk-my-secret-key. Discovery (/.well-known/agent.json) stays public per A2A spec.

Send A2A Message

curl -X POST http://localhost:8000/a2a \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "message/send",
    "id": "1",
    "params": {
      "message": {
        "role": "user",
        "parts": [{"type": "text", "text": "Hello!"}]
      }
    }
  }'

Response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "message": {
      "role": "agent",
      "parts": [{"type": "text", "text": "Hello! How can I help you?"}]
    }
  }
}

Python Client

import requests

# Get Agent Card
response = requests.get("http://localhost:8000/.well-known/agent.json")
agent_card = response.json()
print(f"Agent: {agent_card['name']}")

# Send Message
message = {
    "jsonrpc": "2.0",
    "method": "message/send",
    "id": "1",
    "params": {
        "message": {
            "role": "user",
            "parts": [{"type": "text", "text": "Hello!"}]
        }
    }
}
response = requests.post("http://localhost:8000/a2a", json=message)
print(response.json())

Troubleshooting

Issue	Fix
Port in use	lsof -i :8000
Missing deps	pip install "praisonaiagents[os]"
No API key	export OPENAI_API_KEY="your-key"
Agent Card 404	Check router is included in app

Related

• A2A API Reference - Full A2A endpoint documentation
• AGUI Server - Deploy as AGUI server
• Agents Server - Deploy as HTTP server