Beyond the Protocol Wars: How MCP, UCP, and AP2 Work Together

Developers often misunderstand MCP, UCP, and AP2 as competing standards, but they're actually complementary protocol layers in the AI commerce stack. Based on adoption data from 3,643+ verified UCP stores, these protocols work together seamlessly—with MCP handling tool invocation, UCP defining the commerce contract, and AP2 managing payment authorization. Understanding this layered architecture clarifies technology decisions and prevents costly implementation mistakes.