MCP vs A2A, implemented side by side.

A University of York / Aston group built the same software-engineering coordination scenario twice, once on MCP and once on Agent2Agent, evaluating discoverability, messaging, conversations, async communication, observability, interoperability and access control. MCP: lighter implementation, lower coordination complexity, but conversational state and task lifecycle become application code you write. A2A: richer native stateful multi-turn support at substantially greater implementation cost. They're careful to frame it as one coordination pattern rather than a general ranking, which is the honesty missing from most protocol advocacy. (arXiv 2607.23884)