json-graphql-server is a library that generates a fully functional GraphQL API from a JSON data source, primarily used for mocking and prototyping. It infers a GraphQL schema from sample data, including types, fields, relationships (via `_id` suffixes), and generates queries (single, all, meta) and mutations (create, update, delete) for each entity. The system supports filtering with full-text search, range filters, and pagination, as well as sorting. It can be deployed as an Express middleware, a standalone CLI server, or a client-side mock that intercepts XMLHttpRequests, making it suitable for both backend prototyping and frontend testing without a live server. The architecture is modular, with separate introspection, schema building, resolver, and server integration layers, all built on top of the official `graphql-js` library.