# browser_close_tab

Close a browser tab by tab id

Agent View of the PolicyLayer registry record for `browser_close_tab`. HTML page: https://policylayer.com/tools/cowork-os/browser-close-tab

## Facts

- Tool: `browser_close_tab`
- Server: CoWork OS (`CoWork-OS/CoWork-OS`) — https://policylayer.com/tools/cowork-os.md
- Homepage: https://github.com/CoWork-OS/CoWork-OS
- Risk category: Execute (High risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Rate-limited

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "browser_close_tab",
    "arguments": {}
  }
}
```

## Why browser_close_tab is rated High

Closing a browser tab is a browser action that can cause irreversible loss of unsaved data or session state. While it does not delete stored data, it executes an external operation with potential side effects (lost form data, interrupted processes), placing it in Execute. Severity is medium because the blast radius is limited to a single tab but unsaved work could be lost.

From the tool's own definition: "'Close a browser tab by tab id' — triggers an external browser operation that terminates a tab, which is not reversible if unsaved state is lost"

## Use case

AI agents invoke browser_close_tab to trigger actions in CoWork OS. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.

## Recommended policy (PolicyLayer)

Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches CoWork OS:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "browser_close_tab": {
      "limits": [
        {
          "counter": "browser_close_tab_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}
```

## Other tools on CoWork OS (341)

- `cancel_agent` — Destructive — https://policylayer.com/tools/cowork-os/cancel-agent.md
- `cancel_video_generation_job` — Destructive — https://policylayer.com/tools/cowork-os/cancel-video-generation-job.md
- `cloud_sandbox_delete` — Destructive — https://policylayer.com/tools/cowork-os/cloud-sandbox-delete.md
- `delete_file` — Destructive — https://policylayer.com/tools/cowork-os/delete-file.md
- `disable_macos_launch_agents` — Destructive — https://policylayer.com/tools/cowork-os/disable-macos-launch-agents.md
- `domain_dns_delete` — Destructive — https://policylayer.com/tools/cowork-os/domain-dns-delete.md
- `google-workspace.calendar_event_delete` — Destructive — https://policylayer.com/tools/cowork-os/google-workspace.calendar-event-delete.md
- `google-workspace.slides_delete_slide` — Destructive — https://policylayer.com/tools/cowork-os/google-workspace.slides-delete-slide.md
- `google-workspace.tasks_clear_completed` — Destructive — https://policylayer.com/tools/cowork-os/google-workspace.tasks-clear-completed.md
- `google-workspace.tasks_delete` — Destructive — https://policylayer.com/tools/cowork-os/google-workspace.tasks-delete.md
- `google-workspace.tasks_lists_delete` — Destructive — https://policylayer.com/tools/cowork-os/google-workspace.tasks-lists-delete.md
- `kg_delete_edge` — Destructive — https://policylayer.com/tools/cowork-os/kg-delete-edge.md
- `kg_delete_entity` — Destructive — https://policylayer.com/tools/cowork-os/kg-delete-entity.md
- `skill_delete` — Destructive — https://policylayer.com/tools/cowork-os/skill-delete.md
- `supermemory_forget` — Destructive — https://policylayer.com/tools/cowork-os/supermemory-forget.md
- `blender.render_view` — Execute — https://policylayer.com/tools/cowork-os/blender.render-view.md
- `browser_act_batch` — Execute — https://policylayer.com/tools/cowork-os/browser-act-batch.md
- `browser_attach` — Execute — https://policylayer.com/tools/cowork-os/browser-attach.md
- `browser_back` — Execute — https://policylayer.com/tools/cowork-os/browser-back.md
- `browser_click` — Execute — https://policylayer.com/tools/cowork-os/browser-click.md
- `browser_close` — Execute — https://policylayer.com/tools/cowork-os/browser-close.md
- `browser_drag` — Execute — https://policylayer.com/tools/cowork-os/browser-drag.md
- `browser_emulate` — Execute — https://policylayer.com/tools/cowork-os/browser-emulate.md
- `browser_evaluate` — Execute — https://policylayer.com/tools/cowork-os/browser-evaluate.md
- `browser_fill` — Execute — https://policylayer.com/tools/cowork-os/browser-fill.md
- `browser_forward` — Execute — https://policylayer.com/tools/cowork-os/browser-forward.md
- `browser_handle_dialog` — Execute — https://policylayer.com/tools/cowork-os/browser-handle-dialog.md
- `browser_hover` — Execute — https://policylayer.com/tools/cowork-os/browser-hover.md
- `browser_navigate` — Execute — https://policylayer.com/tools/cowork-os/browser-navigate.md
- `browser_press` — Execute — https://policylayer.com/tools/cowork-os/browser-press.md
- …and 311 more: https://policylayer.com/tools/cowork-os.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=cowork-os · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/cowork-os