UCP and MCP solve different problems. MCP is for context access; UCP is for transaction execution.
Quick decision guide: If you need to act (buy, book, refund), start with UCP. If you need to read (files, DB, CRM), start with MCP. For the deep dive, see UCP vs MCP (Deep Dive).
Figure: Context vs action stack.
| Dimension | MCP | UCP | | --- | --- | --- | | Primary goal | Provide context/data to agents | Execute commerce actions | | Typical use | Read, search, retrieve | Buy, book, refund | | Direction | Inbound information | Outbound action |
A typical agent flow uses MCP to read context (calendar, files, CRM) and UCP to act on that context (purchase, booking, checkout).