Declare an account flagged duplicate the primary of its group: the flag and the pointer swap, this row goes back to ok, the row it duplicated becomes the duplicate pointing here. Nothing moves (merge_companies is the separate act). Reversible: call it on the other row. A row not flagged answers already_primary true. When NOT: moving the leads onto the real account (merge_companies); asking which is primary (duplicate_of_sid on get_company).

Contract:

• MCP tool make_company_primary, registry package mcp.playtables/companies, mount playtables.people.
• Operation action, response envelope action.
• Flags: none.