People keep comparing protocols like they're rivals. MCP vs A2A. AG-UI vs A2UI. That framing is wrong.
Think of it like the networking stack. TCP/IP handles packets. HTTP handles requests. HTML handles content. Each layer does one job and stays out of the others' way. Agent protocols work the same.
Six protocols. One flow. Each layer does exactly one job — and you only adopt the layers you need.
You ask your agent for running shoes under €150. Six protocols collaborate to deliver one tap-to-buy experience. Click Run example to walk through it.
"ACP" now means two unrelated things, which is causing real confusion. IBM's Agent Communication Protocol merged into A2A in August 2025 and is effectively gone. But OpenAI and Stripe co-developed a separate Agentic Commerce Protocol that powers Instant Checkout in ChatGPT — and this one is a direct competitor to UCP, not a complement. The reality of the commerce layer is split between UCP and ACP depending on which platform is driving the transaction. Treat UCP as one of two coexisting options here, not the standard.
The Linux Foundation's Agentic AI Foundation (AAIF), co-founded by OpenAI, Anthropic, Google, Microsoft, AWS and Block, now governs both MCP and A2A, with around 150 member organisations. The "MCP vs A2A" framing is doubly wrong — the same foundation runs both, and AAIF treats WebMCP, MCP and A2A as a three-layer foundation stack alongside each other.
Worth knowing alongside this list even though it isn't strictly a protocol. AGENTS.md is a markdown convention for telling coding agents how to work in your repo — install steps, test commands, code-style notes, what's safe to refactor. It hit ~60,000 projects within its first few months. Sibling to README.md; every coding agent now reads it as part of bootstrapping context. If your repo has Claude Code, Cursor or similar in it, an AGENTS.md is now table stakes.
Start simple. Add layers as the agent grows.
| If your agent… | Add |
|---|---|
| Just calls tools | MCP |
| Coordinates with other agents | MCP + A2A |
| Has a user-facing UI | MCP + A2A + AG-UI |
| Renders rich interfaces (forms, charts, cards) | + A2UI |
| Handles money or signed authorisations | + AP2 |
| Drives commerce flows across merchants | + UCP |
For Aiske.ai specifically: MCP is where we live today — Claude through MCP into Slack, M365, Sentry, Atlassian, GitHub, ELK, Figma, Miro, HubSpot, Intercom, plus the Internal AI Agent's MCP server exposing the data lake. AG-UI is the next natural layer as Aiske 2.0 shifts to chat-driving-forms (workflow.show frames into a guided form on the mobile app). A2A becomes relevant the moment Aiske needs to delegate to a specialist agent — Theo's Neo4j agent for relationship questions, or a sales-side agent for pipeline lookups. UCP, AP2, WebMCP and NLWeb are largely irrelevant for now: we don't transact on farmers' behalf, and our agent surfaces are inside our own apps rather than the open web.