Agent2Agent (A2A) with a2a-sdk and Http2

Continuing with A2A evaluation next up is a2a-sdk (unrelated to previously evaluated a2a-server). This evaluation is largely based on getting the hello world from the a2a-samples project working as per the instruction of a2a-protocol. With additional, integration with other Http2 based non Python clients.

(I) Installation

pip install a2a-sdk 

# uvicorn python-dotenv (packages existing) 

# For Http2 support 

pip install hypercorn 

pip install h2==4.2.0 (See Issue 1 at the end & the bug details) 

git clone https://github.com/a2aproject/a2a-samples.git -b main --depth 1

(II) Replace uvicorn server with hypercorn (support for Http2) 

The a2a-samples make use of the uvicorn python server. However, uvicorn is a Http1.x compliant server and doesn't support Http2. Keep seeing the following messages if client requests from Http2: 

"WARNING:  Unsupported upgrade request. "

In order to support a wider & more updated category of clients, uvicorn is replaced with a hypercorn which is Http2 compliant.

In order to switch to hypercorn, the following changes are done to _main_.py of helloworld python project: 

#import uvicorn
 

# Use Hypercorn for Http2
import asyncio
from hypercorn.config import Config
from hypercorn.asyncio import serve

 ....

    config = Config()
    config.bind="127.0.0.1:8080"  # Binds to all interfaces on port 8080

    asyncio.run(serve(server.build(), config))
   # uvicorn.run(server.build(), host='127.0.0.1', port=8080, log-level='debug') 

(III) Run helloworld

python a2a-samples/samples/python/agents/helloworld/__main__.py 

(IV) View AgentCard

Open in the browser or via curl:

curl http:///127.0.0.1:8080/.well-known/agent-card.json

Response: 

{"capabilities":{"streaming":true},"defaultInputModes":["text"],"defaultOutputModes":["text"],"description":"Just a hello world agent","name":"Hello World Agent","preferredTransport":"JSONRPC","protocolVersion":"0.3.0","skills":[{"description":"just returns hello world","examples":["hi","hello world"],"id":"hello_world","name":"Returns hello world","tags":["hello world"]}],"supportsAuthenticatedExtendedCard":true,"url":"http://127.0.0.1:8080/","version":"1.0.0"} 

For the Authorized Extended Agent Card:

curl -H "Authorization: Bearer dummy-token-for-extended-card" --http2 http://127.0.0.1:8080/agent/authenticatedExtendedCard 

Response: 

{"capabilities":{"streaming":true},"defaultInputModes":["text"],"defaultOutputModes":["text"],"description":"The full-featured hello world agent for authenticated users.","name":"Hello World Agent - Extended Edition","preferredTransport":"JSONRPC","protocolVersion":"0.3.0","skills":[{"description":"just returns hello world","examples":["hi","hello world"],"id":"hello_world","name":"Returns hello world","tags":["hello world"]},{"description":"A more enthusiastic greeting, only for authenticated users.","examples":["super hi","give me a super hello"],"id":"super_hello_world","name":"Returns a SUPER Hello World","tags":["hello world","super","extended"]}],"supportsAuthenticatedExtendedCard":true,"url":"http://127.0.0.1:8080/","version":"1.0.1"} 

(V) Send/ Receive message to Agent

curl -H "Content-Type: application/json"  http:///127.0.0.1:8080 -d '{"jsonrpc":"2.0","id":"ee22f765-0253-40a0-a29f-c786b090889d","method":"message/send","params":{"message":{"role":"user","parts":[{"text":"hello there!","kind":"text"}],"messageId":"ccaf4715-712e-40c6-82bc-634a7a7136f2","kind":"message"},"configuration":{"blocking":false}}}' 

Response: 

 {"id":"ee22f765-0253-40a0-a29f-c786b090889d","jsonrpc":"2.0","result":{"kind":"message","messageId":"d813fed8-58cd-4337-8295-6282930d4d4e","parts":[{"kind":"text","text":"Hello World"}],"role":"agent"}}

(VI) Send/ Receive via Http2

curl -iv --http2 http://127.0.0.1:8080/.well-known/agent-card.json

& 

curl -iv --http2  -H "Content-Type: application/json"  http://127.0.0.1:8080 -d '{"jsonrpc":"2.0","id":"ee22f765-0253-40a0-a29f-c786b090889d","method":"message/send","params":{"message":{"role":"user","parts":[{"text":"dragons and wizards","kind":"text"}],"messageId":"ccaf4715-712e-40c6-82bc-634a7a7136f2","kind":"message"},"configuration":{"blocking":false}}}'

(The responses are the same as shown above)

(VII) Send/ Receive from Java client

TBD

(VIII) Issues 

Issue 1: Compatibility issue with hypercorn (ver=0.17.3) & latest h2 (ver=4.3.0)

Ran in to the issue in the mentioned here:

    |   File "/home/algo/Tools/venv/langvang/lib/python3.13/site-packages/hypercorn/protocol/h2.py", line 138, in initiate
    |     event = h2.events.RequestReceived()
    | TypeError: RequestReceived.__init__() missing 1 required keyword-only argument: 'stream_id' 

Issue was resolved by downgrading to h2 (ver=4.2.0).