---
title: The Human Model
description: How Cortex models AI agents as compositions of human-like traits, skills, and behaviors.
---

Cortex takes a fundamentally different approach to AI agent design. Instead of writing system prompts imperatively ("You are a helpful assistant that..."), you declare an agent's identity using the same building blocks that make humans unique.

## Philosophy

People are not defined by a single instruction. They are the product of:

- **Skills** they have learned (what they can do)
- **Personality traits** that shape how they work
- **Behavioral habits** that emerge from experience
- **Thinking patterns** that guide their reasoning
- **Communication preferences** that define their voice
- **Perceptual filters** that determine what they notice

Cortex makes each of these a first-class, composable entity.

## The seven aspects

| Aspect | Package | Go type | Description |
|--------|---------|---------|-------------|
| [Skill](/docs/cortex/human-model/skills) | `skill` | `skill.Skill` | Capabilities, tools, and knowledge |
| [Trait](/docs/cortex/human-model/traits) | `trait` | `trait.Trait` | Personality dimensions on bipolar axes |
| [Behavior](/docs/cortex/human-model/behaviors) | `behavior` | `behavior.Behavior` | Condition-triggered action patterns |
| [Cognitive Style](/docs/cortex/human-model/cognitive) | `cognitive` | `cognitive.Style` | Phase-based thinking strategies |
| [Communication Style](/docs/cortex/human-model/communication) | `communication` | `communication.Style` | Tone, formality, verbosity |
| [Perception](/docs/cortex/human-model/perception) | `perception` | `perception.Model` | Attention filters and focus |
| [Persona](/docs/cortex/human-model/personas) | `persona` | `persona.Persona` | The complete identity composition |

## Composition hierarchy

Skills, Traits, and Behaviors are **standalone entities** stored independently with their own CRUD APIs. They are composed together through a **Persona**, which references them by name.

Cognitive Style, Communication Style, and Perception are **value objects** embedded directly in the Persona struct.

The **Agent Config** then references a Persona (persona mode) or defines its own system prompt and tools (flat mode).

```
Agent Config
  └── Persona (via PersonaRef)
        ├── Skills[]       (standalone entities, referenced by name)
        ├── Traits[]       (standalone entities, referenced by name)
        ├── Behaviors[]    (standalone entities, referenced by name)
        ├── CognitiveStyle (embedded value object)
        ├── CommunicationStyle (embedded value object)
        └── Perception     (embedded value object)
```

## Declarative vs imperative

Traditional approach (imperative):
```
You are a senior software engineer. Be thorough and methodical.
Focus on security issues. Use a professional but friendly tone.
Always check the code before suggesting changes.
```

Cortex approach (declarative):
```go
persona := &persona.Persona{
    Identity: "A senior software engineer with 10+ years of experience",
    Skills:   []persona.SkillAssignment{{SkillName: "code-review"}},
    Traits:   []persona.TraitAssignment{{TraitName: "thoroughness"}},
    Behaviors: []string{"verify-before-suggest"},
    CommunicationStyle: communication.Style{
        Tone: "professional", Formality: 0.7,
    },
}
```

The declarative approach is composable, reusable, and version-controlled. Change one trait and it updates every agent that uses it.