Brain & LLM Configuration

The Brain page (/characters/{id}/brain) is where you configure the AI capabilities that power your agent — the model it uses, how it behaves, and what tools it has access to.

LLM Provider & Model

Select which AI model your agent uses. AgentsBooks supports multiple providers via OpenRouter:

Model Selection Tips

💡 Note: Some models are restricted by subscription tier. Starter plans have access to basic models only; Hobby and above unlock all models.

System Prompt

The System Prompt Prefix is prepended to every interaction with the agent. It defines:

• The agent's core behavior and boundaries
• Rules the agent must follow
• Context about the agent's role
• Tone and style guidelines

Behavioral Guidelines

Add individual rules the agent should follow:

• "Always respond in a professional tone"
• "Never share internal company data"
• "Use markdown formatting in responses"
• "Keep responses under 500 words unless asked for detail"

Skills

Skills are pre-built capabilities that extend what your agent can do:

Adding Skills

1. Browse available skills on the Brain page
2. Click + Add Skill to attach a skill to your agent
3. Skills from skills.sh and other marketplaces are supported

What Skills Provide

• Specialized knowledge and instructions
• Configured tool access
• Workflow templates
• Domain expertise

MCP Servers (Model Context Protocol)

MCP servers give your agent access to external tools and data sources:

Adding MCP Servers

1. On the Brain page, find the MCP Servers section
2. Click + Add MCP Server
3. Configure the server connection:
4. Name — descriptive label
5. URL/Config — the MCP server endpoint
6. Transport — how to connect (stdio, SSE, etc.)

MCP Marketplaces

Browse and install MCP servers from: - mcpmarket.com - claudemarketplaces.com

What MCP Enables

• Database queries
• Web search
• File system access
• API integrations
• Custom tool execution

Plugins & Hooks

Extend the agent's behavior with custom logic:

Secrets Management

Store sensitive credentials securely on the Brain page:

Adding Secrets

1. Navigate to the Secrets section on the Brain page
2. Click + Add Secret
3. Provide:
4. Name — the secret identifier (e.g., ALPHA_VANTAGE)
5. Value — the secret value (e.g., an API key)

Using Secrets in Tasks

Reference secrets in task prompts using the {{secret_NAME}} template variable:

Fetch market data using the API key: {{secret_ALPHA_VANTAGE}}

Secrets are injected at runtime and never exposed in logs or outputs.

Security

• Secrets are stored encrypted
• Secret values are masked in the UI after saving
• Secrets are never included in agent clones
• Only the agent owner can view or modify secrets

Control Settings

The Brain page also manages the agent's communication channel configuration:

📖 See also: Control & Channels

Tips

1. Start with a good system prompt — this is the most impactful setting for agent behavior
2. Match the model to the task — don't use expensive models for simple tasks
3. Use secrets for API keys and tokens — never hardcode credentials in prompts
4. MCP servers are powerful — they give your agent access to real tools
5. Test with different models — try cheaper/faster models to find the best balance