typefirst

Typefirst is a software development approach that treats type information and data contracts as primary artifacts in the design process. In typefirst practice, developers define explicit types, schemas, and interfaces before implementing behavior, using these contracts to drive API design, data validation, and code generation. The goal is to reduce ambiguity and enable tooling such as type checkers, validators, and client libraries to verify correctness early.

Key principles include starting with schemas or interface definitions (for example OpenAPI schemas or GraphQL types), designing around stable data contracts, and iterating on types alongside tests rather than code alone. Type safety, clear boundaries between components, and compatibility guarantees are emphasized. The approach complements contract-first or API-first design and is compatible with strongly typed languages and type-driven development workflows.

Applications and examples: In API design, teams draft JSON schemas or OpenAPI contracts before implementing endpoints. In front-end and back-end systems, types define data exchange between modules. In data modeling, schemas guide database design and validation rules. Tools such as OpenAPI, GraphQL, Protocol Buffers, or TypeScript type definitions are often used to express and enforce the contracts.

Origin and reception: The term "typefirst" is informal and not standardized; it arises from broader trends toward API-first design, contract-first development, and type-driven tooling. Proponents cite improved maintainability, better refactoring safety, and earlier error detection; critics warn that excessive upfront typing can slow iteration and may be overkill for dynamic contexts.

See also: Type-driven development, API-first design, Contract-first design, OpenAPI, GraphQL, Protocol Buffers.