How to Build An Agent

My TypeScript implementation of an AI agent powered by Claude, inspired by Thorsten Ball's Amp blog post.

Features

• File Operations: Read, list, edit, and create files in your working directory
• Interactive Chat: Natural language interface with Claude (Aura)
• Tool System: Extensible architecture for adding new capabilities
• Type Safety: Full TypeScript support with runtime validation

Prerequisites

• Bun (JavaScript runtime & package manager)
• Anthropic API key

Installation

bun install

Setup

Set your Anthropic API key as an environment variable:

export ANTHROPIC_API_KEY="your-api-key-here"

Usage

Development Mode (with hot reload)

bun run dev

Production Mode

bun start

Build for Distribution

bun run build

Available Tools

The agent comes with four core tools:

read_file

Read the contents of any file in the working directory.

list_directory

List files and directories at a given path.

edit_file

Make edits to text files by replacing specific text strings.

create_file

Create new files with specified content.

Example Session

You: what files are in this directory?

tool: list_directory({"dir_path":"."})

Aura: I can see several files in the current directory:
- README.md
- package.json
- tsconfig.json
- agent.ts - Main agent implementation
- toolRegistry.ts - Tool definitions
- fileUtils.ts - File operation utilities

You: create a hello.js file that prints hello world

tool: create_file({"file_path":"hello.js","content":"console.log('Hello, World!');"})

Aura: I've created a hello.js file that prints "Hello, World!" when run with Node.js.

You:

Architecture

• agent.ts - Main agent implementation with conversation loop
• toolRegistry.ts - Tool definitions and registry
• fileUtils.ts - File system utility functions

Adding New Tools

1. Add your tool definition to toolRegistry.ts:

{
  name: "my_tool",
  description: "Description of what the tool does",
  args: z.object({
    param: z.string(),
  }),
  execute: myToolFunction,
}

2. Implement the tool function in fileUtils.ts or create a new utility file