A key difference between MCP and A2A that is apparent to me after building with MCP and now reading the material on A2A:
MCP is solving specific problems people have in practice today. LLMs need access to data that they weren't trained on, but that's really hard because there's a millions different ways you could RAG something. So MCP defines a standard by which LLMs can call APIs through clients. (and more).
A2A solves a marketing problem that Google is chasing with technology partners.
I think I can safely say which one will still be around in 6 months, and it's not the one whose contributors all work for the same company.
MCP is solving specific problems people have in practice today. LLMs need access to data that they weren't trained on, but that's really hard because there's a millions different ways you could RAG something. So MCP defines a standard by which LLMs can call APIs through clients. (and more).
A2A solves a marketing problem that Google is chasing with technology partners.
I think I can safely say which one will still be around in 6 months, and it's not the one whose contributors all work for the same company.