list_streams

THE RISK

Low Risk

Why list_streams needs a policy

list_streams is a straightforward query that retrieves metadata about existing streams without creating, modifying, deleting, or executing any operations. It matches the Read category definition of retrieving or querying data with no side effects.

From the tool's definition Tool description states it 'lists all streams from KurrentDB' — a pure retrieval operation with no side effects.

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

POLICY

How to control list_streams

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

policy.json

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

list_streams 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 KurrentDB 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

More KurrentDB MCP Server tools

Execute build_projection This function takes a user prompt of what they think a projection should do and then asks Write create_projection create_projection Write update_projection This function is called when a user wants to update a projection. Write write_events_to_stream write_events_to_stream Read get_projections_status Get the status and statistics of a projection in KurrentDB. Read read_stream read_stream Read test_projection This function is called to get guidelines to test a projection.

All 8 KurrentDB MCP Server tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

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_streams

What does the list_streams tool do? +

This function lists all streams from KurrentDB. It is categorised as a Read tool in the KurrentDB MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_streams? +

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

What risk level is list_streams? +

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

Can I rate-limit list_streams? +

Yes. Add a rate_limit block to the list_streams 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_streams completely? +

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

list_streams is provided by the KurrentDB MCP Server MCP server (kurrent-io/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 KurrentDB MCP Server tool call.

Start from KurrentDB 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 →