set_contains

THE RISK

Low Risk

Why set_contains needs a policy

This tool performs a membership check (read/query) on a set data structure, returning a boolean result with no side effects. It only reads data to verify existence of a member.

From the tool's definition Check if member exists in set

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

POLICY

How to control set_contains

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 set_contains:

policy.json

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

set_contains 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

Related tools and policies

More Prometheus MCP Server tools

Destructive bulk_delete_by_criteria bulk_delete_by_criteria Destructive cache_delete Delete a value from the cache. Destructive cache_delete_many Delete multiple values from the cache. Destructive cache_delete_multi Delete multiple values from the cache (alias for delete_many). Destructive delete delete Destructive delete_access_key delete_access_key Destructive delete_agent_runtime delete_agent_runtime Destructive delete_agent_runtime_endpoint delete_agent_runtime_endpoint

All 805 Prometheus 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 set_contains

What does the set_contains tool do? +

Check if member exists in set. 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 set_contains? +

Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for set_contains: 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 set_contains? +

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

Can I rate-limit set_contains? +

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

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

set_contains 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 →