MCP
MCP — the Model Context Protocol — is an open standard for connecting AI applications to external systems: data sources, tools and workflows. It is not a payment protocol. It belongs in a payments glossary because x402 defines a transport for it: a payment can travel over MCP with no HTTP status code involved.
The protocol describes itself as an open-source standard for connecting AI applications to external systems, with the connecting side named the AI application and the connected side an MCP server exposing data, tools or prompts. Its stewardship is formal and stated: the project is established as Model Context Protocol a Series of LF Projects, LLC, with a published maintainer hierarchy. Changes to the specification are made through Specification Enhancement Proposals rather than by direct commit.
The reason it appears here is that x402 defines an MCP transport beside its HTTP one. A client meeting a paid resource through MCP exchanges the same payment fields, without the HTTP 402 response an outside observer could read. The payment is real, and the status code is not there to see.
It is also a different thing from MPP, which two similar abbreviations make easy to miss. MPP is a payment protocol carried over HTTP; MCP is a connection standard for AI applications. One resource can speak both, and an operator choosing between them is not making one choice.
→ probe402 answers the same lookup over MCP as it does over HTTP, and what that surface serves is set out in the method.
Sources
- What is the Model Context Protocol?Model Context Protocol
- Governance and stewardshipModel Context Protocol
- The transport specifications directoryx402 Foundation