# check_mqtt

Connect to an MQTT broker and send a CONNECT packet (v3.1.1). Checks for a CONNACK response and decodes the return code. port: 1883 (plain) or 8883 (TLS). Does not authenticate (anonymous connect). Returns whether the broker accepted the connection and its return code.

Agent View of the PolicyLayer registry record for `check_mqtt`. HTML page: https://policylayer.com/tools/aaronckj-mcp-nettools/check-mqtt

## Facts

- Tool: `check_mqtt`
- Server: Mcp Nettools (`aaronckj/mcp-nettools`) — https://policylayer.com/tools/aaronckj-mcp-nettools.md
- Homepage: https://github.com/aaronckj/mcp-nettools
- 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": "check_mqtt",
    "arguments": {}
  }
}
```

## Why check_mqtt is rated High

This tool actively establishes a network connection to an external MQTT broker and sends protocol packets, triggering external operations. It is not merely reading local data — it performs an outbound connection and interaction with a remote service. This goes beyond Read into Execute territory, as it initiates a session with an external system.

From the tool's own definition: "Connect to an MQTT broker and send a CONNECT packet (v3.1.1). Checks for a CONNACK response"

## Use case

AI agents invoke check_mqtt to trigger actions in Mcp Nettools. 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 Mcp Nettools:

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

## Other tools on Mcp Nettools (234)

- `http_delete` — Destructive — https://policylayer.com/tools/aaronckj-mcp-nettools/http-delete.md
- `check_rdp` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/check-rdp.md
- `http_post` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/http-post.md
- `ping` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/ping.md
- `port_scan` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/port-scan.md
- `speedtest` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/speedtest.md
- `traceroute` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/traceroute.md
- `wake_on_lan` — Execute — https://policylayer.com/tools/aaronckj-mcp-nettools/wake-on-lan.md
- `arp_table` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/arp-table.md
- `bgp_lookup` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/bgp-lookup.md
- `cert_check` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/cert-check.md
- `cert_check_bulk` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/cert-check-bulk.md
- `check_actual_budget` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-actual-budget.md
- `check_adguard` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-adguard.md
- `check_alertmanager` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-alertmanager.md
- `check_anythingllm` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-anythingllm.md
- `check_appwrite` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-appwrite.md
- `check_archivebox` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-archivebox.md
- `check_audiobookshelf` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-audiobookshelf.md
- `check_authelia` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-authelia.md
- `check_authentik` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-authentik.md
- `check_baikal` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-baikal.md
- `check_bazarr` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-bazarr.md
- `check_beszel` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-beszel.md
- `check_bitwarden` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-bitwarden.md
- `check_bookstack` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-bookstack.md
- `check_calibre_web` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-calibre-web.md
- `check_cassandra` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-cassandra.md
- `check_changedetection` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-changedetection.md
- `check_checkmk` — Read — https://policylayer.com/tools/aaronckj-mcp-nettools/check-checkmk.md
- …and 204 more: https://policylayer.com/tools/aaronckj-mcp-nettools.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=aaronckj-mcp-nettools · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/aaronckj-mcp-nettools