shop_mcp_server: MCP server and RAG in Ruby on Rails

An MCP server in Ruby on Rails that lets Claude read a store's products, orders and inventory, place orders with approval, and search by meaning.

7 tools, 2 resources and 1 prompt. Six tools are read-only; the one write tool (create order) is marked destructive, so Claude asks the user before running it. An order and its stock changes run in one database transaction. Semantic search (RAG) uses Voyage AI embeddings in a pgvector column. Tested with RSpec, MCP Inspector and Claude as a live connector.

Stack: Ruby 4.0, Rails 8.1, official MCP Ruby SDK, PostgreSQL, pgvector, Voyage AI, RSpec. Case study: https://mjesar.github.io/projects/shop_mcp_server/ Code: https://github.com/mjesar/shop_mcp_server