Ruby gem by the speaker of a wroclove.rb 2026 lightning talk. Declarative way to build self-documenting REST API endpoints: define a service with metadata/URLs, declare endpoints with optional query/payload schemas, and compose logic as a railway-oriented pipeline of steps (with sub-pipelines for complex cases). Schemas are themselves steps in the pipeline, so you can validate before/after other steps (e.g. for authentication). Supports authentication schemes defined by the OpenAPI specification, content negotiation (send JSON, get HTML back and vice versa), file uploads. Mounted as a Rack app, it serves as a one-to-one mapping to an OpenAPI spec and generates the spec automatically (usable with Swagger UI). Additional helper decorates the same REST service definition as an MCP endpoint — one line turns a self-documenting REST API into an MCP server whose tools map to the existing endpoints, letting Claude use the API conversationally.