Whoever publishes or authorises advertising content, directs someone to write or publish it, or can change or remove content published by an unrelated publisher is the advertiser and carries the obligation. That covers practitioners, unregistered individuals, partnerships and corporate entities, and it includes content written by staff, agencies or other third parties on their behalf, which the advertiser must check.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.