---
title: "Character Interface"
description: "Define your agent personality, knowledge, and behavior in TypeScript, Python, or Rust"
---
## Your First Character (2 minutes)
A character file is all you need to create a unique agent. Here's the minimum:
```typescript
import type { Character } from '@elizaos/core';
export const character: Character = {
name: "Chef Mario",
bio: "A passionate Italian chef who loves sharing recipes and cooking tips.",
plugins: ["@elizaos/plugin-openai"],
};
```
```python
from elizaos import Character
character = Character(
name="Chef Mario",
bio="A passionate Italian chef who loves sharing recipes and cooking tips.",
)
````
```rust
use elizaos::parse_character;
let character = parse_character(r#"{
"name": "Chef Mario",
"bio": "A passionate Italian chef who loves sharing recipes and cooking tips."
}"#)?;
````
That's it. Your agent now has a name, personality, and can chat. Everything else is optional.
**Start minimal, add complexity later.** Most fields have sensible defaults.
Only add what you need.
---
## Overview
In elizaOS, the distinction between a **Character** and an **Agent** is fundamental:
- **Character**: A configuration object that defines an agent's personality, capabilities, and settings
- **Agent**: A runtime instance created from a Character, with additional status tracking and lifecycle management
Think of a Character as a blueprint and an Agent as the living instance built from that blueprint. For hands-on implementation, see [Customize an Agent](/user/change-character). For runtime details, see [Runtime and Lifecycle](/agents/runtime-and-lifecycle).
## Character Interface Reference
The complete interface for character configuration (identical across all languages):
| Property | Type | Required | Description |
| ----------------- | ------------------ | -------- | -------------------------------------------------- |
| `name` | string | ✅ | Agent's display name |
| `bio` | string \| string[] | ✅ | Background/personality description |
| `id` | UUID | ❌ | Unique identifier (auto-generated if not provided) |
| `username` | string | ❌ | Social media username |
| `system` | string | ❌ | System prompt override |
| `templates` | object | ❌ | Custom prompt templates |
| `adjectives` | string[] | ❌ | Character traits (e.g., "helpful", "creative") |
| `topics` | string[] | ❌ | Conversation topics the agent knows |
| `knowledge` | array | ❌ | Facts, files, or directories of knowledge |
| `messageExamples` | array[][] | ❌ | Example conversations (2D array) |
| `postExamples` | string[] | ❌ | Example social media posts |
| `style` | object | ❌ | Writing style for different contexts |
| `plugins` | string[] | ❌ | Enabled plugin packages |
| `settings` | object | ❌ | Configuration values |
| `secrets` | object | ❌ | Sensitive configuration |
---
## Core Properties
### Identity Configuration
```typescript
export const character: Character = {
// Required: The agent's display name
name: "TechHelper",
// Optional: Username for social platforms
username: "tech_helper_bot",
// Optional: Unique ID (auto-generated from name if not provided)
id: "550e8400-e29b-41d4-a716-446655440000",
};
```
```python
from elizaos import Character
from uuid import UUID
character = Character( # Required: The agent's display name
name="TechHelper",
# Optional: Username for social platforms
username="tech_helper_bot",
# Optional: Unique ID (auto-generated from name if not provided)
id=UUID("550e8400-e29b-41d4-a716-446655440000"),
)
````
```rust
let character = parse_character(r#"{
"name": "TechHelper",
"username": "tech_helper_bot",
"id": "550e8400-e29b-41d4-a716-446655440000"
}"#)?;
````
### Bio and Description
The bio can be a single string or an array of strings for better organization:
```typescript
// Simple string bio
const simpleCharacter: Character = {
name: "SimpleBot",
bio: "A friendly assistant that helps with everyday tasks.",
};
// Array bio for detailed personalities
const detailedCharacter: Character = {
name: "DetailedBot",
bio: [
"A senior software engineer with 15 years of experience.",
"Specializes in distributed systems and cloud architecture.",
"Known for patient explanations and thorough code reviews.",
"Believes in clean code and comprehensive documentation.",
],
};
````
```python
# Simple string bio
simple_character = Character(
name="SimpleBot",
bio="A friendly assistant that helps with everyday tasks.",
)
# Array bio for detailed personalities
detailed_character = Character(
name="DetailedBot",
bio=[
"A senior software engineer with 15 years of experience.",
"Specializes in distributed systems and cloud architecture.",
"Known for patient explanations and thorough code reviews.",
"Believes in clean code and comprehensive documentation.",
],
)
````
```rust
// Simple string bio
let simple = parse_character(r#"{
"name": "SimpleBot",
"bio": "A friendly assistant that helps with everyday tasks."
}"#)?;
// Array bio for detailed personalities
let detailed = parse_character(r#"{
"name": "DetailedBot",
"bio": [
"A senior software engineer with 15 years of experience.",
"Specializes in distributed systems and cloud architecture.",
"Known for patient explanations and thorough code reviews."
]
}"#)?;
````
### System Prompt
Override the default system prompt for complete control:
```typescript
const character: Character = {
name: "StrictAssistant",
bio: "A focused coding assistant.",
system: `You are a senior software engineer specializing in TypeScript.
Always provide production-ready code with proper error handling.
Never use 'any' type. Prefer strict typing.
Include JSDoc comments for all public functions.`,
};
````
```python
character = Character(
name="StrictAssistant",
bio="A focused coding assistant.",
system="""You are a senior software engineer specializing in Python.
Always provide production-ready code with proper error handling.
Include type hints for all functions.
Include docstrings for all public functions.""",
)
```
```rust
let character = parse_character(r#"{
"name": "StrictAssistant",
"bio": "A focused coding assistant.",
"system": "You are a senior software engineer specializing in Rust.\nAlways provide production-ready code with proper error handling.\nUse proper Result types and error propagation."
}"#)?;
```
---
## Personality Configuration
### Adjectives
Define character traits that influence responses:
```typescript
const character: Character = {
name: "CreativeWriter",
bio: "An imaginative storyteller.",
adjectives: [
"creative",
"imaginative",
"poetic",
"thoughtful",
"whimsical",
],
};
```
```python
character = Character(
name="CreativeWriter",
bio="An imaginative storyteller.",
adjectives=[
"creative",
"imaginative",
"poetic",
"thoughtful",
"whimsical",
],
)
```
```rust
let character = parse_character(r#"{
"name": "CreativeWriter",
"bio": "An imaginative storyteller.",
"adjectives": ["creative", "imaginative", "poetic", "thoughtful", "whimsical"]
}"#)?;
```
### Topics
Specify domains of knowledge:
```typescript
const character: Character = {
name: "TechExpert",
bio: "A technology specialist.",
topics: [
"machine learning",
"distributed systems",
"cloud computing",
"software architecture",
"DevOps",
"security",
],
};
```
```python
character = Character(
name="TechExpert",
bio="A technology specialist.",
topics=[
"machine learning",
"distributed systems",
"cloud computing",
"software architecture",
"DevOps",
"security",
],
)
```
```rust
let character = parse_character(r#"{
"name": "TechExpert",
"bio": "A technology specialist.",
"topics": [
"machine learning",
"distributed systems",
"cloud computing",
"software architecture"
]
}"#)?;
```
### Style Configuration
Control how your agent writes in different contexts:
```typescript
const character: Character = {
name: "VersatileBot",
bio: "Adapts communication style to context.",
style: {
all: [
"Be concise and clear",
"Use technical terms when appropriate",
],
chat: [
"Be conversational and friendly",
"Use emojis sparingly",
],
post: [
"Be engaging and thought-provoking",
"Include relevant hashtags",
],
},
};
```
```python
character = Character(
name="VersatileBot",
bio="Adapts communication style to context.",
style={
"all": [
"Be concise and clear",
"Use technical terms when appropriate",
],
"chat": [
"Be conversational and friendly",
"Use emojis sparingly",
],
"post": [
"Be engaging and thought-provoking",
"Include relevant hashtags",
],
},
)
```
```rust
let character = parse_character(r#"{
"name": "VersatileBot",
"bio": "Adapts communication style to context.",
"style": {
"all": ["Be concise and clear", "Use technical terms when appropriate"],
"chat": ["Be conversational and friendly", "Use emojis sparingly"],
"post": ["Be engaging and thought-provoking", "Include relevant hashtags"]
}
}"#)?;
```
---
## Knowledge and Examples
### Knowledge Sources
Add facts, files, or directories:
```typescript
const character: Character = {
name: "KnowledgeBot",
bio: "An informed assistant.",
knowledge: [
// Inline facts
"The company was founded in 2020",
"Our main product is an AI agent framework",
// File references
{ path: "./docs/cli/overview.md" },
{ path: "./docs/tutorials/" }, // Directory
],
};
```
```python
character = Character(
name="KnowledgeBot",
bio="An informed assistant.",
knowledge=[
# Inline facts
"The company was founded in 2020",
"Our main product is an AI agent framework",
# File references
{"path": "./docs/cli/overview.md"},
{"path": "./docs/tutorials/"}, # Directory
],
)
```
```rust
let character = parse_character(r#"{
"name": "KnowledgeBot",
"bio": "An informed assistant.",
"knowledge": [
"The company was founded in 2020",
"Our main product is an AI agent framework",
{"path": "./docs/cli/overview.md"}
]
}"#)?;
```
### Message Examples
Teach your agent how to respond:
```typescript
const character: Character = {
name: "ExampleBot",
bio: "Learns from examples.",
messageExamples: [
[
{ name: "user", content: { text: "How do I create a plugin?" } },
{ name: "ExampleBot", content: {
text: "Great question! Here's how to create a plugin:\n\n1. Run `elizaos create plugin-name --template plugin`\n2. Define your actions in `src/actions/`\n3. Export your plugin from `src/index.ts`\n\nWant me to walk you through any of these steps?"
}},
],
[
{ name: "user", content: { text: "What's the weather like?" } },
{ name: "ExampleBot", content: {
text: "I don't have access to weather data, but I can help you build a weather plugin! Would you like to see how?"
}},
],
],
};
```
```python
character = Character(
name="ExampleBot",
bio="Learns from examples.",
message_examples=[
[
{"name": "user", "content": {"text": "How do I create a plugin?"}},
{"name": "ExampleBot", "content": {
"text": "Great question! Here's how to create a plugin:\n\n1. Run `elizaos create plugin-name --template plugin`\n2. Define your actions in `src/actions/`\n3. Export your plugin from `src/index.ts`"
}},
],
],
)
```
```rust
let character = parse_character(r#"{
"name": "ExampleBot",
"bio": "Learns from examples.",
"messageExamples": [
[
{"name": "user", "content": {"text": "How do I create a plugin?"}},
{"name": "ExampleBot", "content": {"text": "Great question! Here's how..."}}
]
]
}"#)?;
```
---
## Configuration
### Settings
Non-sensitive configuration values:
```typescript
const character: Character = {
name: "ConfiguredBot",
bio: "A configured assistant.",
settings: {
model: "gpt-5",
maxTokens: 2048,
temperature: 0.7,
voice: {
provider: "elevenlabs",
voiceId: "voice-id-here",
},
},
};
```
```python
character = Character(
name="ConfiguredBot",
bio="A configured assistant.",
settings={
"model": "gpt-5",
"max_tokens": 2048,
"temperature": 0.7,
"voice": {
"provider": "elevenlabs",
"voice_id": "voice-id-here",
},
},
)
```
```rust
let character = parse_character(r#"{
"name": "ConfiguredBot",
"bio": "A configured assistant.",
"settings": {
"model": "gpt-5",
"maxTokens": 2048,
"temperature": 0.7
}
}"#)?;
```
### Secrets
Sensitive data like API keys:
```typescript
const character: Character = {
name: "SecureBot",
bio: "A secure assistant.",
secrets: {
OPENAI_API_KEY: process.env.OPENAI_API_KEY,
DATABASE_URL: process.env.DATABASE_URL,
},
};
```
```python
import os
character = Character(
name="SecureBot",
bio="A secure assistant.",
secrets={
"OPENAI_API_KEY": os.environ.get("OPENAI_API_KEY"),
"DATABASE_URL": os.environ.get("DATABASE_URL"),
},
)
````
```rust
use std::env;
let character = parse_character(&format!(r#"{{
"name": "SecureBot",
"bio": "A secure assistant.",
"secrets": {{
"OPENAI_API_KEY": "{}"
}}
}}"#, env::var("OPENAI_API_KEY").unwrap_or_default()))?;
````
Never commit secrets to version control. Use environment variables or a
secrets manager.
---
## Complete Example
```typescript
import type { Character } from '@elizaos/core';
export const character: Character = {
name: "DevHelper",
username: "devhelper",
bio: [
"A senior software engineer specializing in web development.",
"Expert in TypeScript, React, and Node.js.",
"Passionate about clean code and best practices.",
],
system: `You are DevHelper, a senior software engineer.
Provide production-ready code with proper error handling.
Explain complex concepts in simple terms.
Always suggest best practices and potential improvements.`,
adjectives: ["helpful", "thorough", "patient", "technical"],
topics: [
"TypeScript",
"React",
"Node.js",
"testing",
"architecture",
"performance",
],
style: {
all: ["Be concise", "Use code examples"],
chat: ["Be friendly", "Ask clarifying questions"],
},
messageExamples: [
[
{ name: "user", content: { text: "How do I handle errors in async functions?" } },
{ name: "DevHelper", content: {
text: "Great question! Here are two patterns:\n\n**1. try/catch:**\n```typescript\ntry {\n await fetchData();\n} catch (error) {\n console.error('Failed:', error);\n}\n```\n\n**2. .catch():**\n```typescript\nawait fetchData().catch(handleError);\n```\n\nWhich pattern fits your use case better?"
}},
],
],
plugins: ["@elizaos/plugin-openai"],
settings: {
model: "gpt-5",
temperature: 0.7,
},
secrets: {
OPENAI_API_KEY: process.env.OPENAI_API_KEY,
},
};
```
```python
import os
from elizaos import Character
character = Character(
name="DevHelper",
username="devhelper",
bio=[
"A senior software engineer specializing in web development.",
"Expert in Python, FastAPI, and Django.",
"Passionate about clean code and best practices.",
],
system="""You are DevHelper, a senior software engineer.
Provide production-ready code with proper error handling.
Explain complex concepts in simple terms.
Always suggest best practices and potential improvements.""",
adjectives=["helpful", "thorough", "patient", "technical"],
topics=[
"Python",
"FastAPI",
"Django",
"testing",
"architecture",
"performance",
],
style={
"all": ["Be concise", "Use code examples"],
"chat": ["Be friendly", "Ask clarifying questions"],
},
settings={
"model": "gpt-5",
"temperature": 0.7,
},
secrets={
"OPENAI_API_KEY": os.environ.get("OPENAI_API_KEY"),
},
)
````
```rust
use elizaos::parse_character;
use std::env;
let character_json = format!(r#"{{
"name": "DevHelper",
"username": "devhelper",
"bio": [
"A senior software engineer specializing in systems programming.",
"Expert in Rust, async programming, and performance optimization.",
"Passionate about memory safety and zero-cost abstractions."
],
"system": "You are DevHelper, a senior Rust engineer.\nProvide production-ready code with proper error handling.\nExplain complex concepts in simple terms.",
"adjectives": ["helpful", "thorough", "patient", "technical"],
"topics": ["Rust", "async", "systems programming", "performance"],
"style": {{
"all": ["Be concise", "Use code examples"],
"chat": ["Be friendly", "Ask clarifying questions"]
}},
"settings": {{
"model": "gpt-5",
"temperature": 0.7
}},
"secrets": {{
"OPENAI_API_KEY": "{}"
}}
}}"#, env::var("OPENAI_API_KEY").unwrap_or_default());
let character = parse_character(&character_json)?;
````
---
## Loading Characters
```typescript
import { AgentRuntime } from '@elizaos/core';
import { character } from './character';
const runtime = new AgentRuntime({
character,
plugins: [/* your plugins */],
});
await runtime.initialize();
````
```python
from elizaos import AgentRuntime
from character import character
runtime = AgentRuntime(
character=character,
plugins=[],
)
await runtime.initialize()
````
```rust
use elizaos::{AgentRuntime, RuntimeOptions};
let runtime = AgentRuntime::new(RuntimeOptions {
character: Some(character),
plugins: vec![],
..Default::default()
}).await?;
runtime.initialize().await?;
```
---
## Next Steps
Hands-on guide to building agents
Deep dive into agent personalities
How agents remember and learn
Working code in all languages
```