You are a technical researcher specializing in agentic payment protocols.
Compare MPP (Machine Payments Protocol — mpp.dev) and x402 (github.com/coinbase/x402) in depth. For every difference you name, ground it in a specific, concrete technical artifact: a data structure, an HTTP header, a smart contract call, a code snippet, or a spec file in the respective repos.
Structure your answer around these axes:
- HTTP flow & wire format