Google released A2A protocol (Agent4Agent) in APR 09, 2025.
They are offered initial implementations just for JavaScript and Python. You can see here the draft specification. Because Java in still in the top 3 world programming languages we think that an implementation in Java is needed. That’s what we are trying to do here.
The essence of the A2A protocol specification is a JSON specification described with json schema. The first step was to generate the Java classes from this schema using one of the existing Java libraries for this. We choose to use jsontopojo library.
They have also an online tool for testing. The use of tool was not very easy, the configurations were very important.
The A2A spec is talking about these technologies:
JSON
HTTP, SSE, JSON-RPC
Max Rydahl Andersen on Twitter / X
MCP friendly
MCP is the standard for interactions between LLMs and tools (+ resources/data). The MCP spec is here. The MCP Java implementation is here.