# Tools

A tool is a callable capability that agents can use during task execution. Each tool lives in its own directory under `tools/` and is defined by a `TOOL.md` file and an `index.ts` (or `index.js`) entry point.

Tools are loaded by the `tool-loader` extension at startup and registered as callable functions. They appear in the agent's system prompt and can be invoked by name.

## File Structure

```
tools/
  <tool-name>/
    TOOL.md       # Metadata and documentation
    index.ts      # Implementation (required)
```

Both files are required. The loader skips directories missing either `TOOL.md` or an entry file.

## TOOL.md Format

A tool file has two parts: **frontmatter** (YAML metadata) and **body** (Markdown documentation).

### Frontmatter

```yaml
---
name: tool_name
label: Tool Name
description: What the tool does and when the agent should use it.
version: 1
language: typescript
inputs:
  param_name:
    type: string
    description: What this parameter is for.
  optional_param:
    type: number
    description: An optional parameter.
    optional: true
  secret_param:
    type: string
    description: A sensitive value (e.g., API token).
    optional: true
    sensitive: true
  mode:
    type: enum
    values: single,batch
    description: Choose between modes.
---
```

#### Fields

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `name` | string | yes | Identifier for the tool (used in tool calls). Use `snake_case`. |
| `label` | string | no | Human-readable display name. Defaults to `name` if omitted. |
| `description` | string | yes | What the tool does. This appears in the agent's system prompt — make it specific enough for the agent to know when to use it. |
| `version` | integer | no | Version number. Used by `sync-tools` to detect updates — bump when changing the tool. |
| `language` | string | no | Implementation language: `typescript`, `bash`, or `python`. Defaults to `typescript`. |
| `inputs` | object | no | Input parameters the tool accepts. Keys are parameter names. |

#### Input Fields

Each input is a key under `inputs:` with these properties:

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `type` | string | yes | Parameter type: `string`, `number`, `boolean`, or `enum`. |
| `description` | string | yes | What this parameter is for. Shown to the agent. |
| `optional` | boolean | no | Whether the parameter is optional. Defaults to required. |
| `sensitive` | boolean | no | Mark sensitive values (tokens, passwords). Prevents logging. |
| `values` | string | no | Comma-separated allowed values when `type` is `enum`. |
| `default` | any | no | Default value if not provided. |

### Body

The body is Markdown documentation that the agent sees when the tool is loaded. Include:

- **Title** — `# Tool Name`
- **Authentication** — How credentials are resolved (env vars, integrations, etc.)
- **Usage** — How to call the tool and what parameters to pass.
- **Examples** — Common usage patterns.
- **Error Handling** — What errors can occur and what they mean.
- **Notes** — Limits, billing, external links.

## index.ts Format

The entry file must export an `execute` function:

```typescript
type ToolResult = {
  content: Array<{ type: string; text: string }>;
  isError?: boolean;
};

type OnUpdate = (partial: { content: Array<{ type: string; text: string }> }) => void;

export async function execute(
  toolCallId: string,
  params: Record<string, unknown>,
  signal: AbortSignal | undefined,
  onUpdate?: OnUpdate,
): Promise<ToolResult> {
  // Implementation here
}
```

### Parameters

| Parameter | Description |
|-----------|-------------|
| `toolCallId` | Unique ID for this tool call. |
| `params` | Input values from the agent, matching the `inputs` defined in TOOL.md. |
| `signal` | AbortSignal for cancellation. |
| `onUpdate` | Callback for streaming progress updates to the agent during long operations. |

### Return Value

Return a `ToolResult` object:
- `content` — Array of content blocks. Usually one `{ type: 'text', text: '...' }`.
- `isError` — Set `true` to indicate failure. The agent sees the error and can react.

### Progress Updates

Use `onUpdate` to stream status during long-running operations:

```typescript
onUpdate?.({ content: [{ type: 'text', text: 'Processing step 2 of 5...' }] });
```

### Authentication

Tools should resolve credentials internally, not require the agent to pass them. Pattern:

1. Check for an explicit parameter override (e.g., `params.api_token`)
2. Fall back to an environment variable (e.g., `process.env.OFFICER_APIFY_TOKEN`)
3. Return a helpful error if neither is available

Environment variables are set by `pi-bridge.ts` from the integration config stored in the database (Settings → Integrations).

### Runtime Environment

Tools run inside sandboxed containers using **Node.js** (not Bun). Do not use Bun-specific APIs like `Bun.sleep`, `Bun.file`, etc. Use Node.js equivalents:

- `setTimeout` / `setInterval` for delays
- `fs.readFileSync` / `fs.writeFileSync` for file I/O
- `fetch` (available in Node 18+) for HTTP requests

### Large Output

If a tool may return large data (e.g., API responses with many items), provide an `output_path` parameter. When set, save the data to the file and return a summary instead:

```typescript
if (params.output_path) {
  writeFileSync(params.output_path, JSON.stringify(items, null, 2));
  return { content: [{ type: 'text', text: `${items.length} items saved to ${params.output_path}` }] };
}
```

This prevents flooding the agent's context window with raw data.

## Sync and Discovery

Tools are synced from `seed/tools/` to `DATA_PATH/tools/` at server startup by `sync-tools.ts`. The sync is version-based — it only overwrites when the seed version is higher than the target version. Always bump `version` in the frontmatter when updating a tool.

The `tool-loader` extension discovers tools from directories listed in the `PI_TOOLS_DIRS` environment variable (colon-separated). Only `DATA_PATH/tools/` is mounted into containers — `seed/tools/` is not directly accessible at runtime.

## Existing Tools

| Tool | Description |
|------|-------------|
| `gmail` | Read Gmail messages, threads, labels via Google API |
| `web_search` | Search the web via SearXNG |
| `web_fetch` | Fetch and extract content from URLs |
| `browser` | Control a Chrome browser via Browser Relay |
| `apify` | Run any Apify actor (web scraping, social media data) |
| `convert_audio_to_mp3` | Convert audio files to MP3 via ffmpeg |
| `ffmpeg` | Run ffmpeg/ffprobe commands for any audio/video processing |
| `ocr` | Optical character recognition on images |
| `email_db` | Query the synced email database |