list_alerts

Retrieve alerts from Mackerel. 🔍 USE THIS TOOL WHEN USERS: - Check currently active alerts - Get a list of alerts including closed alerts <examples> Get opening alerts \

ServerMackerel MCP Server
CategoryRead

How to control list_alerts ↓

WHAT IT DOES

What list_alerts does on Mackerel MCP Server

AI agents call list_alerts to retrieve information from Mackerel MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

THE RISK

Low Risk

Why list_alerts needs a policy

This tool retrieves or lists existing alert information from the Mackerel monitoring platform. It has no capability to create, modify, delete, or trigger actions—it only queries and returns data. This is a classic Read operation with low severity since it merely accesses monitoring information already available within the system.

From the tool's definition Tool name 'list_alerts' and description 'Retrieve alerts from Mackerel' indicate a query operation that fetches and returns alert data without modification or side effects.

Documented attack patterns abuse exactly the kind of access list_alerts gives an agent:

POLICY

How to control list_alerts

PolicyLayer is an MCP gateway — it sits between your AI agents and Mackerel MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_alerts:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_alerts": {}
  }
}

list_alerts is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Mackerel MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_alerts

What does the list_alerts tool do? +

Retrieve alerts from Mackerel. 🔍 USE THIS TOOL WHEN USERS: - Check currently active alerts - Get a list of alerts including closed alerts <examples> Get opening alerts \. It is categorised as a Read tool in the Mackerel MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_alerts? +

Register the Mackerel MCP Server MCP server in PolicyLayer and add a rule for list_alerts: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Mackerel MCP Server. Nothing to install.

What risk level is list_alerts? +

list_alerts is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_alerts? +

Yes. Add a rate_limit block to the list_alerts rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block list_alerts completely? +

Set action: deny in the PolicyLayer policy for list_alerts. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides list_alerts? +

list_alerts is provided by the Mackerel MCP Server MCP server (mackerelio-labs/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mackerel MCP Server tool call.

Start from Mackerel MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →

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16 Mackerel MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.