# API First Everyone **MUST** follow the **API First** principle. The API first principle is an extension of design-first principle. Therefore, a development of an API **MUST** always start with API design without any upfront coding activities. **API design** (e.g., description, schema) **is the master of truth, not the API implementation.** API implementation **MUST** always be compliant to a particular API design which represents the [contract](/api-guidelines/general-guidelines/contract.md) between API, and it's consumer. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://adidas.gitbook.io/api-guidelines/general-guidelines/api-first.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.