A few months ago I was wiring up a multi-agent pipeline where one agent writes code, another reviews it, and a third deploys it. Everything worked great in the demo.

Then I asked a simple question: if the review agent says "looks good," how do I actually know it ran the tests?

I couldn't answer it. Neither could MCP, A2A, or any framework I looked at.

The gap nobody talks about

MCP connects agents to tools. A2A connects agents to agents. These solve connectivity. But connectivity isn't accountability.