ListDbInstances | PolicyLayer

WHAT IT DOES

What ListDbInstances does on Amazon Bedrock Knowledge Base Retrieval MCP Server

AI agents call ListDbInstances to retrieve information from Amazon Bedrock Knowledge Base Retrieval 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 ListDbInstances needs a policy

This is a read-only operation that retrieves metadata about existing database instances. It has no side effects, cannot modify data, and poses minimal risk even if misused by an agent—the worst outcome would be information disclosure of instance names or configurations already accessible to the authenticated user.

From the tool's definition Tool name 'ListDbInstances' and description 'List all Timestream for InfluxDB DB instances' indicate a retrieval operation that queries and returns a list of database instances without modifying, executing, or deleting anything.

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 Amazon Bedrock Knowledge Base Retrieval 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 Amazon Bedrock Knowledge Base Retrieval 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.

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EXPLORE

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Go deeper

Roll out MCP under one policy → Per-person scoped tokens, one central policy, and full audit across every server your team connects.
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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

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 Amazon Bedrock Knowledge Base Retrieval MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on ListDbInstances? +

Register the Amazon Bedrock Knowledge Base Retrieval 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 Amazon Bedrock Knowledge Base Retrieval 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 Amazon Bedrock Knowledge Base Retrieval MCP Server MCP server (awslabs.bedrock-kb-retrieval-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 Amazon Bedrock Knowledge Base Retrieval MCP Server tool call.

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

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