This tool models core D&D 5e (2014) action economy rules. Haste grants one extra action restricted to Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object (PHB p.250). Subclass features (e.g. Eldritch Knight spell slots, Arcane Trickster), feats, magic items, and multiclassing are not tracked. The bonus action spell restriction (PHB p.203) applies whenever any leveled spell is cast as a bonus action, regardless of source. Reaction spells used against another creature's action occur on their turn; this tool shows them as your available reaction option for that scenario. "Cast a Spell (Action)" is intentionally generic. Pick Cantrip or a spell level to trigger full validation. This tool is a rules aid, not a replacement for the Player's Handbook or DM judgment.