Adjacent terms name parts of the job: RAG is a retrieval technique the layer operates; MCP standardizes the connection to tools and data; a vector database is one store inside it. The context layer is the whole, run as governed infrastructure for every agent rather than rebuilt per project.
It matters most in regulated industries, where every consequential agent action must be grounded in permitted, current data and reconstructable after the fact — the audit trail regulators and model-risk teams expect.