Contact-first API design focuses on establishing explicit API contracts before development begins, facilitating smoother collaboration between frontend and backend developers. This approach reduces rework and parallelizes development by ensuring both teams have a clear understanding of data requirements and endpoints. Technologies like OpenAPI, GraphQL, gRPC, and tRPC enable this process by providing frameworks for defining and documenting APIs, thus allowing developers to auto-generate client libraries and server code. Each technology offers unique benefits; OpenAPI allows detailed REST API descriptions, GraphQL provides efficient querying of data with a graph-based schema, gRPC uses protocol buffers for binary serialization, and tRPC leverages TypeScript for type-safe APIs. By adopting contract-first API design, teams can effectively use developer tools to prevent errors, improve productivity, and ensure robust validation of requests and data consistency across services.