> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agenticenv.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Tools

> Register built-in and custom tools with approval handlers, authorizers, and dynamic registry patterns

The `agent_with_tools` family demonstrates `WithTools`, `WithToolRegistry`, `WithApprovalHandler`, `ToolAuthorizer`, and the dynamic registry API. Each sub-example isolates one aspect of tool configuration so you can see exactly what each API controls.

Source: [`examples/agent_with_tools/`](https://github.com/agenticenv/agent-sdk-go/tree/main/examples/agent_with_tools)

## Examples in this group

| Directory          | Demonstrates                                                                     |
| ------------------ | -------------------------------------------------------------------------------- |
| `basic`            | Built-in tools — echo, calculator, weather, wikipedia, search with auto-approval |
| `approval`         | `WithApprovalHandler` — approve or reject each tool (`Run`)                      |
| `authorizer`       | `ToolAuthorizer` — programmatic deny before execution                            |
| `custom`           | Custom tool via `WithTools`                                                      |
| `dynamic_registry` | `ToolRegistry().Register` between runs                                           |

## Run

From `examples/`:

```bash theme={null}
go run ./agent_with_tools/basic "What's the weather in Tokyo?"
go run ./agent_with_tools/approval "What is 15 + 27?"
go run ./agent_with_tools/authorizer "Get the protected note for roadmap."
go run ./agent_with_tools/custom "Reverse 'hello world'"
go run ./agent_with_tools/dynamic_registry
```

## Expected output

```
# basic — auto-approval, answer printed directly
The current weather in Tokyo is 18°C, partly cloudy with light winds.

# approval — prompt appears for each tool call
Tool call: calculator({"expression":"15+27"})
Approve? [y/n]: y
15 + 27 = 42

# authorizer — programmatic deny
Access denied: you do not have permission to access the protected note.

# custom — custom Reverse tool
"hello world" reversed is "dlrow olleh"

# dynamic_registry — tool added between runs
[Run 1] No tools available.
[Run 2] reversed: "dlrow olleh"
```

## Learn more

<CardGroup cols={2}>
  <Card title="Tools" icon="wrench" href="/features/tools">
    Registration and execution modes
  </Card>

  <Card title="Approvals" icon="shield-check" href="/features/approvals">
    Approval policies and handlers
  </Card>

  <Card title="Dynamic Capabilities" icon="rotate" href="/advanced/dynamic-capabilities">
    Runtime tool registry
  </Card>
</CardGroup>