Maturity
We have defined a maturity model in order to be able to differentiate between good and bad interfaces. This is an important precondition for the movement to better interfaces by fostering a high demanding API culture.
Table of contents
MUST Continuous improvement of API Maturity
APIs must invest a continuous effort in increasing the maturity of an API according to the API Maturity Model. 
Rational
Higher maturities of interfaces lead to lower costs due to …
- higher speed in the development of API consumers.
- higher reuse coefficient due to better understandability, quality and functional precision.
MUST APIs provide automated tests
An API must provide at least one staging environment with full functionality and close-to-production testdata.
Rational
A production-like testing environment increases …
- speed in implementing new features in the API.
- changeability and maintainability rates.
- operational stability (e.g. less unknown side-effects).