What is gadget?

gadget is a Go library that lets an MCP server ship interactive UI components, like data tables and forms, inside a chat window. MCP, or Model Context Protocol, is a standard that connects AI assistants to external tools and data. With gadget, a developer can build an app that responds to a user request with a full, interactive interface right in the conversation, rather than just plain text. The library provides several ready-made widgets. The Table widget handles typed columns, sorting, filtering, pagination, and row selection with bulk actions. The Form widget supports ten field types, client-side validation, and submit or cancel actions. The Menu widget acts as a launcher grid of tiles, where each tile opens a specific tool. CardList and Card widgets handle collections and single records, with features like scrolling card strips and status badges. The same widget can render in a light or dark theme depending on the host application's appearance. A key feature is that everything is self-contained. All CSS and JavaScript is inlined into the HTML output, with no external files or network requests needed. This means a developer can compile their entire application into a single Go binary, making deployment straightforward. The widgets automatically pick up the host's design tokens, so they match the look of whichever app is rendering them, such as Claude, ChatGPT, or VS Code. The project is currently marked as pre-release, which means its APIs may still change. It includes examples to help developers get started, such as a demo server for listing, editing, and deleting users, and a fake host harness for testing different widget variants in a sandboxed environment. The core runtime works with any Go MCP implementation, and there is a specific adapter for the official Go SDK. The README points to separate documentation files for widget references, theming details, and architecture notes. The project is licensed under MIT.