Kontraktfirst

Kontraktfirst is a design approach used in API development and software integration in which the API contract is created before any server-side implementation. The contract defines the surface of the API: endpoints, operations, request and response formats, validation rules, and error semantics. Contracts are typically expressed in machine-readable specifications such as OpenAPI/Swagger, RAML, or WSDL for SOAP services. The contract-first process serves as a single source of truth that guides both client and server development and can be used to generate skeleton code, tests, and client SDKs.

In practice, kontraktfirst begins with drafting a precise contract, followed by validating it against business requirements and technical constraints. Development teams implement the API logic to satisfy the contract, and downstream clients generate code from the contract. This approach supports early validation, better API governance, and improved interoperability with partners, because consumers rely on a stable contract.

Benefits include improved consistency across services, easier contract testing and contract-driven development, and the ability to simulate or mock services from the contract before backend is available. Potential drawbacks are higher upfront design effort, the need for specialized tooling, and possible drift between the contract and evolving backend if governance is weak.

Kontraktfirst is commonly used in RESTful and SOAP contexts, especially in enterprise environments where standardization and contract governance are priorities.