Writing Custom Tools

Overview

Custom tools are TypeScript/JavaScript definitions that let the LLM call your functions during conversations. The definition is always TS/JS, but can invoke scripts in any language.

When to Use

• Creating a new tool for LLM to call
• Editing or improving an existing tool
• Reviewing tool quality and argument schemas
• Wrapping scripts in other languages (Python, Bash, etc.)

Don't use for: MCP servers (different pattern), plugins (use plugin hooks), or built-in tool configuration.

File Structure