effect-schema-composition

What problem does it solve? Writing correct Effect Schema v4 code requires knowing which composition API to use—Schema.decodeTo for type-changing transformations, .check() for same-type refinements, and SchemaTransformation objects for reusable transforms—and how v4 differs from v3 patterns like Schema.compose and Schema.split. ## Core Features & Use Cases - Schema Composition: Chain multi-stage transformations with Schema.decodeTo and apply sequential refinements with .check() filters. - Built-in and Custom Filters: Use Schema.isXxx() validators, Schema.makeFilter for custom logic with error paths, and SchemaGetter.checkEffect for async validation. - Transformations and Structs: Build reusable SchemaTransformation objects, manipulate structs via mapFields with Struct.pick/omit/assign, and handle optional fields and decoding defaults. - Use Case: When building an API response parser that decodes string IDs to numbers, validates email formats, and transforms nested user objects, this skill provides the exact v4 patterns and a quality checklist to avoid deprecated v3 APIs. ## Quick Start Ask the AI to write an Effect Schema v4 schema that decodes a string to a branded positive integer with validation filters and proper error messages.