Every few weeks someone asks whether MCP replaces REST. It does not. The question is still worth answering carefully, because the line between the two moved in July, and most of the explanations written before then are now describing a protocol that no longer exists.

An HTTP API is a contract between two pieces of software written by people who read documentation. A developer opens the reference, learns that POST /v1/invoices wants a customer ID and an array of line items, writes the call, and ships it. The knowledge lived in a human head at build time and then got frozen into source code. When the endpoint changes, something breaks in production and a person goes and fixes it.