This study aimed to explore how legitimizing institutions create credibility for metrics within their spheres of operation and influence. It specifically examined how three companies—MOZ, SEMRush, and Ahrefs—construct credible narratives to justify the indicators they sell, using a subset of search engine optimization metrics. The theoretical framework employed includes Bourdieu's field theory and Certeau's tactics and strategies, with the methodology being the French discourse analysis of Algirdas Greimas. We observed that legitimizing institutions rely on tactics such as outsourcing responsibility, denying the claims of others, compartmentalizing data, and embracing technological solutionism as postulated by Morozov to affirm their relevance. We also found evidence that the introduction of a new "data" by a legitimizing institution undergoes a process with a certain degree of generalized validation, where the discourse considers the actors involved in its use and interpretation.