aminoxix/schemind

Schemind watches the APIs your application calls and notices when their responses change shape, without you writing or maintaining a schema yourself. You wrap your existing fetch calls with a function it provides, and from then on it quietly learns what each endpoint actually returns. The first time it sees a response it stores that shape as a baseline, then it compares every later call against that baseline and tells you the moment something differs, such as a field disappearing, a type changing, or a value that used to always be present becoming allowed to be empty. Changes are grouped into three levels of severity. A field being removed or a type changing counts as breaking and gets flagged in red. A field becoming nullable or newly required is a warning shown in yellow. A brand new field being added is just informational and shown in blue. You can wire these observations into Slack, GitHub, or your own webhook so a teammate sees the alert instead of it sitting silently in a log. Beyond the plain fetch wrapper, the package includes ready made integrations for Express, Next.js route handlers, Hono, and TanStack Query, so you can drop it into common backend and frontend setups with minimal changes. It also ships a command line tool called schm that can run as a gate in continuous integration, probing your API and failing the build if a breaking change slipped through. That same tool can generate TypeScript types, an OpenAPI spec, JSON Schema, or mock handlers from what it has learned about your API, and it includes a small local dashboard for browsing endpoint health. By default the learned shapes live only in memory and reset when your app restarts, but you can persist them to disk so the same baseline is available the next time your CI pipeline runs. The package requires Node.js version 18 or later and has no runtime dependencies of its own. It works in the browser, at the edge, and in Node.