ListDbInstances

THE RISK

Low Risk

Why ListDbInstances needs a policy

This tool performs a query/list operation to enumerate database instances. It has no side effects—it only retrieves metadata about existing resources. No data is created, modified, deleted, or financial operations are involved. The blast radius of misuse is minimal; an attacker could only discover what DB instances exist, which is reconnaissance-level impact.

From the tool's definition Tool name 'ListDbInstances' and description 'List all Timestream for InfluxDB DB instances' indicate a read-only operation that retrieves information about existing database instances without modification.

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

POLICY

How to control ListDbInstances

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

policy.json

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

ListDbInstances 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 Prometheus 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

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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 ListDbInstances

What does the ListDbInstances tool do? +

List all Timestream for InfluxDB DB instances. It is categorised as a Read tool in the Prometheus MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on ListDbInstances? +

Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for ListDbInstances: 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 Prometheus MCP Server. Nothing to install.

What risk level is ListDbInstances? +

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

Can I rate-limit ListDbInstances? +

Yes. Add a rate_limit block to the ListDbInstances 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 ListDbInstances completely? +

Set action: deny in the PolicyLayer policy for ListDbInstances. 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 ListDbInstances? +

ListDbInstances is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-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 Prometheus MCP Server tool call.

Start from Prometheus 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 →