AI agents call get_promql_label_values to retrieve information from Prometheus MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries Prometheus to retrieve label values, which is a read-only operation with no side effects. Despite the empty description lowering confidence slightly, the name clearly indicates data retrieval. Blast radius is minimal—incorrect label queries do not modify infrastructure or expose sensitive data beyond what Prometheus already exposes to authenticated users.
From the tool's definition Tool name 'get_promql_label_values' indicates retrieval of label values from Prometheus using PromQL; no modification, deletion, or execution of external operations implied.
Documented attack patterns abuse exactly the kind of access get_promql_label_values gives an agent:
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 get_promql_label_values:
{
"version": "1",
"default": "deny",
"tools": {
"get_promql_label_values": {}
}
}get_promql_label_values is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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get_promql_label_values. It is categorised as a Read tool in the Prometheus MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for get_promql_label_values: 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.
get_promql_label_values is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the get_promql_label_values 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.
Set action: deny in the PolicyLayer policy for get_promql_label_values. 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.
get_promql_label_values 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.
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.
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805 Prometheus MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.