Agent2Agent (A2A) with a2a-server

Agent2Agent (A2A) is a protocol for AI agents to communicate amongst themselves. These Agents though built by different vendors by subscribing to the common a2a protocol will have a standardized way of inter-operating.  

Getting going with A2A 

(I) As a starting point got the python a2a-server installed. 

pip install a2a-server

Issue 1: Compatibility issue between latest a2a-server & a2a-json-rpc:

a2a-server & a2a-server also brings in a2a-json-rpc:  but there were compatibility issues between the latest a2a-json-rpc (ver.0.4.0) & a2a-server (ver. 0.6.1)

        ImportError: cannot import name 'TaskSendParams' from 'a2a_json_rpc.spec' (.../python3.13/site-packages/a2a_json_rpc/spec.py) 

Downgrading  a2a-json-rpc to previous 0.3.0 fixed it:

pip install a2a-json-rpc==0.3.0 

(II) To get the a2a-server running a agent.yaml file needs to be built with the configs like host, port, handler, provider, model, etc:

server:
  host: 127.0.0.1
  port: 8080

handlers:
  use_discovery: false
  default_handler: chuk_pirate
  chuk_pirate:
    type: a2a_server.tasks.handlers.chuk.chuk_agent_handler.ChukAgentHandler
    agent: a2a_server.sample_agents.chuk_pirate.create_pirate_agent
    name: chuk_pirate
    enable_sessions: false
    enable_tools: false
    provider: "ollama"
    model: "llama3.2:1b"
    version: "1.0.1"

    agent_card:
      name: Pirate Agent
      description: "Captain Blackbeard's Ghost with conversation memory"
      capabilities:
        streaming: false
        sessions: false
        tools: false 

-- 

Next, start the server using:

a2a-server -c agent.yaml --log-level debug 

(III) Test a2a-server endpoint from browser

Open http://127.0.0.1:8080/ which will lists the different Agents. 

Agent Card(s): 

http://127.0.0.1:8080/chuk_pirate/.well-known/agent.json 

(IV) Issues a2a-server 

Issue 2: Agent Card endpoint url 

Firstly, the Agent Card end point is that this is no longer a valid end point. As per the latest Agent Card protocol the Agent Card needs to be served from the location: http://<base_url>/ .well-known/agent-card.json. 

• agent-card.json (& not agent.json) 
• Without the agent's name (i.e. without chuk_pirate) 

The valid one would looks like:

http://127.0.0.1:8080/chuk_pirate/.well-known/agent.json 

Issue 3: Error message/send not found

The other issue is that the seems to be a lack of support for the method "message/ send"  used to send messages and chat with the agent. The curl request fails with an error: 

curl -iv -H "Content-Type: application/json"  http://127.0.0.1:8080/chuk_pirate -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}}}' 

{"jsonrpc":"2.0","id":"ee22f765-0253-40a0-a29f-c786b090889d","result":null,"error":{"code":-32601,"message":"message/send not found"}} 

Due to all these issues with a2a-server and its lack of documentation there's no clarity on the library. So it's a no-go for the moment atleast.