Marks, labels and certifications and their underlying technical standards are valuable sources for requirements; the organization can reference their criteria in full or in part so that conforming goods can be bought even without the label (with the conformity assessment guidance of 7.3.5), or specify the label itself, considering the number of eligible suppliers so as not to limit competition and any public procurement restrictions; the organization can also ask suppliers and industry associations.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.