Currently, there is a broad range of software development agile approaches mainly based on the values and principles defined in the agile manifesto (AM). However, in many cases, their implementation is carried out informally and without being aligned with the values and principles stated. In practice, practitioners and consultants may lose sight of the AM recommendations, which could jeopardize the companies' agility, therefore, applying an agile approach does not make a company agile. In this article, we present a reference model called AgilityRef, which allows practitioners to support the understanding and implementation of the values and principles of the agile manifesto in the software development processes of a company, this, through twenty-two aspects defined from relations established between principles and values described in the AM and processes elements described in Scrum, XP, and Kanban. The evaluation of AgilityRef was carried out through a focus group where its completeness, understandability, and suitability were evaluated. Our findings suggest good enough acceptance by professionals and consultants who evaluated the proposal. The proposed reference model seems to allow professionals and companies to improve the understanding and implementation in practice of the concept of agility in their companies' software development processes, thus, minimizing the subjectivity and error of their process adoption, implementation, evaluation, and articulation with the principles and values of the agile manifesto.