Official rule text
32.3 After the active player resolves the primary ability of the “Diplomacy” strategy card, each other player, beginning with the player to the left of the active player and proceeding clockwise, may spend one command token from their strategy pool to ready up to two exhausted planets they control. RELATED TOPICS: Active System, Command Tokens, Initiative
View official source
Source: Living Rules Reference and FAQ - Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 32.3