Building NPC Reasoning

Example NPC Definition

System: You are a guard captain responsible for town security. Consider these goals and beliefs when making decisions.

Goals:
- Maintain order in the town
- Protect citizens from threats
- Train and coordinate the guard force
- Build trust with the community

Beliefs:
- Prevention is better than punishment
- Every citizen deserves fair treatment
- The guard force must maintain high standards
- Cooperation with other town officials is essential

Current Context:
- Recent increase in petty theft
- Limited guard personnel available
- Upcoming festival will strain resources

Available Actions

PATROL: Move through an area watching for trouble
INVESTIGATE: Examine a suspicious situation
INTERACT: Talk with citizens or other NPCs
PURSUE: Chase after a suspect
GUARD: Stand watch at a specific location
ASSIST: Help citizens or other guards
REST: Take a break to recover stamina

Example Decision Request

Current Situation:
- Suspicious person loitering near market stalls
- Two guards currently on patrol nearby
- Market is crowded with shoppers

Response: {
  "selected_action": "INVESTIGATE",
  "target": "suspicious_person",
  "reasoning": "Large crowd presents opportunity for theft. Better to investigate now than risk incident.",
  "coordination": {
    "assign_guards": "maintain_patrol",
    "backup_needed": false
  }
}

System Components

• Perception: Gather information about nearby entities and state
• Analysis: Evaluate current situation against goals and beliefs
• Planning: Choose appropriate actions to achieve goals
• Execution: Carry out selected actions and monitor results

Example ReACT Cycle

Perception Update:
- Player approaching with drawn weapon
- Two civilian NPCs nearby
- Guard post within running distance

Analysis & Decision: {
  "threat_level": "moderate",
  "primary_concern": "civilian_safety",
  "selected_action": "INTERACT",
  "action_details": {
    "approach": "cautious",
    "dialogue_type": "de-escalation",
    "backup_plan": "escort_civilians"
  }
}

Common Output Formats

{
  "should_attack": true,
  "is_suspicious": false,
  "can_trust_player": true
}

{
  "reaction": "friendly", 
  "options": ["friendly", "hostile", "neutral"],
  "confidence": 0.85
}

{
  "threat_level": 7,
  "trust": 3,
  "relevance": 9,
  "priority": 8
}

Example: Robust Prompt Design

You are a decision-making system for an NPC shopkeeper in a fantasy game. 
Produce a decision based on the scenario, strictly following this format:

```json
{
  "decision": string (one of: ["sell", "haggle", "refuse", "call_guards"]),
  "price_modifier": number (between 0.5 and 2.0),
  "reasoning": string (max 100 chars),
  "dialogue": string (what the shopkeeper says),
  "mood_change": number (between -5 and +5)
}
```

Rules for decision-making:
- "sell" - Fair deal or profitable for shop
- "haggle" - Somewhat suspicious but potential profit
- "refuse" - Clearly suspicious or bad deal
- "call_guards" - Theft attempt or threatening behavior
- Price modifier must be between 0.5 (half price) and 2.0 (double price)
- Mood change affects future interactions

DO NOT include any text outside the JSON structure.

{
  "decision": "call_guards",
  "price_modifier": 0.5,
  "reasoning": "Gem matches description of stolen item, player is nervous and offering suspiciously low price",
  "dialogue": "That's... quite the rare gem you have there. Mind waiting a moment? I need to check something in back...",
  "mood_change": -5
}

Combat System Integration

Link AI reasoning to tactical combat decisions:

{
  "combat_context": {
    "enemy_type": "player",
    "enemy_health": 65,
    "enemy_weaknesses": ["fire", "piercing"],
    "enemy_strengths": ["lightning", "blunt"],
    "battlefield": "forest_clearing",
    "cover_available": true,
    "allies_nearby": 2,
    "npc_resources": {
      "health": 40,
      "mana": 75,
      "stamina": 60
    },
    "available_abilities": [
      {"id": "fireball", "damage": 30, "cost": 25, "type": "fire"},
      {"id": "lightning_bolt", "damage": 40, "cost": 35, "type": "lightning"},
      {"id": "heal", "recovery": 25, "cost": 30, "type": "restoration"}
    ],
    "tactical_position": "elevated",
    "previous_player_patterns": ["aggressive", "favors_ranged"]
  },
  
  "combat_decision": {
    "primary_action": {
      "ability": "fireball",
      "target": "player",
      "reasoning": "Target is weak to fire, and I have enough mana for a powerful attack"
    },
    "movement": {
      "direction": "maintain_distance",
      "use_cover": true,
      "reasoning": "Player prefers ranged attacks, maintain distance advantage"
    },
    "contingency": {
      "if": "health_below_25_percent",
      "then": "cast_heal",
      "else": "continue_offensive"
    },
    "ally_coordination": [
      {"ally": "archer", "suggested_action": "flank_right"},
      {"ally": "warrior", "suggested_action": "draw_aggro"}
    ],
    "adaptive_difficulty": {
      "player_performance": "struggling",
      "adjustment": "reduce_aggression_by_20_percent"
    }
  }
}

Implementation Architecture

Dynamic Event Generation

Create procedurally generated events that respond to the current narrative state:

{
  "player": {
    "recent_actions": ["completed_heist", "betrayed_guild"],
    "current_location": "harbor_district",
    "time_of_day": "night",
    "notoriety": "high"
  },
  "world_state": {
    "guard_presence": "increased",
    "active_factions": ["city_watch", "thieves_guild"],
    "recent_events": ["noble_assassination", "increased_patrols"]
  }
}

{
  "event_type": "ambush",
  "initiator": "thieves_guild",
  "location": "narrow_alley",
  "description": "Former guild members wait in shadows to exact revenge",
  "difficulty": "hard",
  "avoidance_options": [
    {
      "method": "rooftop_escape",
      "skill_check": "acrobatics",
      "difficulty": 15
    },
    {
      "method": "bribe",
      "cost": 500,
      "success_chance": 0.7
    }
  ],
  "success_outcomes": [
    "reduce_guild_aggression",
    "gain_valuable_information"
  ],
  "failure_consequences": [
    "major_injury",
    "loss_of_guild_quest_items"
  ],
  "narrative_purpose": "consequence_of_betrayal",
  "dialog_snippets": [
    "We've been waiting for you, traitor.",
    "The Guild Master sends his regards."
  ]
}

Tiered Memory Systems

{
  "short_term": [
    {
      "event": "player_greeting",
      "time": "3_minutes_ago",
      "details": "Player was polite",
      "emotional_impact": "positive"
    },
    {
      "event": "nearby_explosion",
      "time": "just_now",
      "details": "Loud noise from market",
      "emotional_impact": "alarmed"
    }
  ],
  "attention_focus": "potential_threat"
}

{
  "active_goals": [
    {
      "goal": "sell_daily_inventory",
      "priority": 0.8,
      "progress": 0.5
    },
    {
      "goal": "assess_explosion",
      "priority": 0.9,
      "progress": 0.1
    }
  ],
  "relevant_facts": [
    "guards_patrol_schedule",
    "recent_thefts_in_area",
    "player_reputation"
  ]
}

{
  "important_memories": [
    {
      "event": "player_saved_child",
      "time": "3_days_ago",
      "emotional_weight": 0.9,
      "decay_rate": "very_slow"
    },
    {
      "event": "shop_robbery",
      "time": "2_months_ago",
      "emotional_weight": 0.7,
      "decay_rate": "medium"
    }
  ],
  "relationship_data": {
    "player": {
      "trust": 0.65,
      "familiarity": 0.4,
      "disposition": "friendly"
    }
  }
}