## Overview

In this example we will guide you through creating custom tools using the Strands Agents `tool()` function. We will build a personal assistant that connects with a local SQLite database to manage appointments.

![Custom Tools Architecture](https://raw.githubusercontent.com/strands-agents/samples/3c9ebca88ad8906ca77147753d951c5e2a7123bd/typescript/01-learn/02-custom-tools/images/agent_with_custom_tools.png)

| Feature | Description |
| --- | --- |
| Custom tools created | create\_appointment, list\_appointments, update\_appointment |
| Agent Structure | Single agent architecture |

## Prerequisites

-   Node.js 22 or later (the version `@strands-agents/sdk` supports)
-   AWS account with Amazon Bedrock access
-   Basic TypeScript knowledge

## Running the Example

```bash
cd typescript/01-learn/02-custom-tools
npm install
npx tsx src/index.ts
```

## Project Structure

```plaintext
src/
├── database/
│   └── AppointmentDatabase.ts    # SQLite data access layer
├── tools/
│   └── AppointmentTools.ts       # Tool definitions factory
└── index.ts                      # Main entry point
```

## Key Concepts

### Class-Based Tool Organization

Tools are organized using a factory class pattern that encapsulates tool creation and database dependencies:

```typescript
export class AppointmentTools {
  constructor(private database: AppointmentDatabase) { }

  getCreateAppointmentTool() {
    return tool({
      name: "create_appointment",
      description: "Create a new personal appointment...",
      inputSchema: z.object({ date, location, title, description }),
      callback: (input) => {
        const id = this.database.createAppointment(...);
        return `Appointment created with ID: ${id}`;
      }
    });
  }

  getAllTools() {
    return [
      this.getCreateAppointmentTool(),
      this.getListAppointmentsTool(),
      this.getUpdateAppointmentTool()
    ];
  }
}
```

### Database Integration

The `AppointmentDatabase` class uses `better-sqlite3` to store appointment information:

```typescript
export class AppointmentDatabase {
  constructor(databasePath: string = "appointments.db") {
    this.db = new Database(databasePath);
    this.initializeTables();
  }

  createAppointment(date, location, title, description): string
  listAppointments(): Appointment[]
  updateAppointment(id, updates): number
}
```

### Agent Configuration

```typescript
const agent = new Agent({
  model: new BedrockModel({
    modelId: "us.anthropic.claude-haiku-4-5-20251001-v1:0",
  }),
  systemPrompt: "You are a helpful personal assistant...",
  tools
});
```

## Additional Resources

-   [Strands Agents Documentation](https://strandsagents.com/latest/)

## Upstream source

- [View this sample at the imported commit](https://github.com/strands-agents/samples/tree/3c9ebca88ad8906ca77147753d951c5e2a7123bd/typescript/01-learn/02-custom-tools)