A2A gives opaque agents a protocol for cross-system collaboration

A2A addresses a different layer from ordinary tool calling: agents built on diverse frameworks and hosted by different organizations need a way to discover each other's capabilities, negotiate interaction modalities, and collaborate on long-running tasks. The repository frames A2A as a protocol for agent-to-agent interoperability while preserving opacity around internal state, memory, and proprietary tools. For builders, the practical takeaway is to evaluate agent systems not only by what tools they can call through MCP, but also by how they communicate and coordinate with other agents across organizational boundaries.