Six agent protocols just launched. Three of them decide which products survive. Here is how to tell which three.

Source: Nate’s Newsletter Date: 2026-05-19 URL: https://natesnewsletter.substack.com/p/agent-protocol-stack-mcp-a2a

Summary

Nate identifies six newly-launched agent protocols and argues only three form the essential stack: MCP (tool/data access), A2A (agent-to-agent delegation), and AG-UI (human oversight). The remaining three (A2UI, AP2, x402) are important but secondary — operating in layers where trust boundaries and payment rails are still being negotiated. Core argument: protocol selection shapes customer experience more than model choice. Builders treating all six equally become paralyzed; failures occur at boundaries that actually matter (security on tool access, approval on long-running work, supervision when agents cross company lines).

Implications

• Feeds the protocol governance thread: Nate’s three-layer stack (MCP + A2A + AG-UI) is the clearest protocol triage framework published. If adopted, it tells builders what to implement first.
• AG-UI as essential is a new claim — human oversight as a protocol layer, not a product feature. Connects to Android Halo (Google’s implementation of agent visibility) and Claude Code’s agent view.
• AP2 relegated to “secondary” despite Google donating it to FIDO and announcing Universal Cart with AP2 at I/O the same day. Nate is saying the payment layer matters but isn’t foundational. The agentic commerce thread should track this tension.
• Ninth domain for Nate: protocol governance (added to the eight tracked).