get-label-values · Prometheus MCP: Risk & Policy

WHAT IT DOES

What get-label-values does on Prometheus

AI agents call get-label-values to retrieve information from Prometheus without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

WHY IT NEEDS A POLICY

Why get-label-values needs a policy

This tool retrieves label values from Prometheus metrics—a read-only query operation with no side effects. It discovers metadata about metric labels, similar to the sibling tools 'get-metadata' and 'get-series'. There is no data creation, modification, deletion, code execution, or financial impact. The blast radius of misuse is minimal—an agent could only retrieve label information that already exists in Prometheus.

From the tool's definition Tool name 'get-label-values' and description 'Get label values for a label name' indicate a retrieval operation. This is a metadata query against Prometheus that returns information about available label values without modifying any data.

Attacks that exploit this kind of access

Questions about get-label-values

What does the get-label-values tool do? +

Get label values for a label name. It is categorised as a Read tool in the Prometheus MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get-label-values? +

Register the Prometheus MCP server in PolicyLayer and add a rule for get-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. Nothing to install.

What risk level is get-label-values? +

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

Can I rate-limit get-label-values? +

Yes. Add a rate_limit block to the get-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.

How do I block get-label-values completely? +

Set action: deny in the PolicyLayer policy for get-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.

What MCP server provides get-label-values? +

get-label-values is provided by the Prometheus MCP server (mateusdata/prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.