Interaction capability is the 2023 name for what the earlier model called usability. The draft gives it eight measure families, the largest group in clause 6. The eight families run from recognising that the product is appropriate, through learning it, operating it, being protected from error, being engaged, being included, being assisted and understanding what it is doing. Eight families is a statement in itself: interaction is not one number. The 2023 model added user controllability to this characteristic, and the draft gives it no separate measure family, so a team that needs it must define a local measure. The human factors terms, accessibility, usability and user, are defined in clause 3 and they keep these measures tied to people rather than to interface features.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.