MythxEngine

Break complete information into mysterious fragments, creating revelatory discovery.

Advance to the next turn in combat

Pause an active clock. Time-based triggers will not fire while paused.

Connect abstract information to a PC's backstory, making it personally relevant.

Spend 2 stress to add +1d6 bonus to a failed or partial roll. Can trigger trauma if stress exceeds max. Returns an envelope with `outcome` ('pushed' or 'trauma_gained') and a one-line `summary` as the headline; mechanical detail is in `result` (including `previousOutcome` → `newOutcome`, the re-derived outcome tier for the pushed margin), stress/trauma changes in `state_delta`.

Fast deterministic world pack lookup. Use for finding monsters, NPCs, locations, items, etc. Automatically detects entity type and does fuzzy name matching. Pure function lookup (~5ms) with no LLM overhead.

Log a search that found nothing. Critical for hypothesis testing.

Recover stress during rest. Short rest recovers 2 stress, long rest recovers all stress.

Remove a condition from a character. Accepts the condition id OR its display name (case-insensitive). No-op if the condition isn't on the character.

Remove a deadline by ID

Remove an item from a character's inventory. For stackable items, can remove a specific quantity. Automatically unequips if equipped.

Mark a human player as awaiting input for their turn

Spend stress to reduce a consequence. Roll ability to potentially reduce cost. Minor=1, Moderate=2, Severe=3 base cost. Pass `damage` when the consequence is HP damage — the tool then applies the mechanical effect itself (successful resist halves it, failed resist lands in full; set `alreadyApplied` if the damage already hit HP so it refunds the reduction). Returns an envelope with `outcome` ('reduced', 'absorbed', or 'trauma_gained') and a one-line `summary` as the headline; stress/trauma/HP changes in `state_delta`.

Resume a paused clock.

Resume an interrupted world generation session. Analyzes session state to report progress and optionally reset incomplete steps.

Make a hidden situation clock visible to players on their HUD. Call this exactly when your narration reveals the threat or deadline to the players — not before. Until revealed, clocks are GM-only state and may tick in secret.

Mark a portable clue as discovered.

Mark a lead as discovered by the players.

Perform a custom test defined in the world pack rules (e.g., panic check, sanity roll). Returns success/failure, any table rolls, and effects to apply.

Roll dice using standard notation (e.g., '2d6+3', 'd20', '4d6'). Optionally use session RNG for determinism.

Roll initiative for all combatants and set turn order

Perform a skill or ability test for a character. Rolls d20 + ability + skill + modifiers vs difficulty. Supports advantage/disadvantage. Returns an envelope with `outcome` (five-tier) and a one-line `summary` as the headline; mechanical detail is in `result`, follow-up moves in `suggested_next`.

Save generated book content to a file.

Save LLM-generated content back to the session. Call this after executing a generation prompt. Accepts JSON or XML formatted results.

Save the generated rulebook content to files.

Adjust the difficulty of an existing encounter.

Search for leads by keyword across all lead information.

Search session notes by keyword or tags

Sell an item from the character's inventory for gold. Default sell price is 50% of item value.

Update the session's current party location. The locationId must exist in the active world pack. Drives the persistent scene panel in the UI.

Set the play mode for a session. 'interactive' prompts the player for decisions, 'auto' plays all characters autonomously. Persists across context compaction.

Sets game time (for initialization/GM override)

Start adding new content to an existing world pack. Returns generation prompts for the requested content types.

Initialize combat with characters and enemies. Returns an envelope with `outcome: 'combat_started'` and a one-line `summary` as the headline; combatant lists in `result`, combat state in `state_delta`. Always follow with `roll_initiative` (also surfaced in `suggested_next.next_action`).

Start a structured NPC dialogue. Loads NPC data from the world pack, sets the UI to dialogue stage with portrait and response choices.

Begin tracking a mystery. Define the truth (GM-only) to enable hypothesis testing.

Start a situation clock. The clock tracks what happens if PCs don't intervene.

Begin turn-based coordination for multi-player gameplay

Record an AI player's decided action

Record a human player's chosen action

Get suggestions for how to naturally deliver a clue in the current context.

Get suggestions for moving the investigation forward.

Suggest ways to naturally surface leads pointing to a target situation. Supports the Three Clue Rule.

Recommend how to transition to the next meaningful moment. Based on the Alexandrian principle: 'Cut to the next meaningful choice.'

Initiate a rest sequence for the party. Recovers HP and stress, advances game time, and optionally clears conditions. Sets the UI stage to 'rest'. Returns an envelope with `outcome` ('short_rest', 'long_rest', or 'camp_rest') and a one-line `summary` as the headline; per-character mechanics in `result.results`, totals in `state_delta`.

Record the result of testing a hypothesis. Supports the 'null result' principle.

Manually advance a clock to its next stage. Use for event-based triggers or GM override.

Transfer an item between characters or to/from party inventory. Automatically unequips if the item is equipped.

Package information as a valuable discovery - a physical item, document, or reward.

Unequip an item from an equipment slot. The item remains in inventory.