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prometheus-mcp-server

by weetime

get-label-values

Retrieve all values associated with a specific label name in Prometheus. Use this to explore label dimensions and filter metric queries by available values.

Instructions

Get label values for a label name

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
labelNameYesLabel name to get values for

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

C2.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It states 'Get' implies a read operation but doesn't specify whether this requires authentication, has rate limits, returns paginated results, or what format the values are in (e.g., strings, arrays). This is inadequate for a tool with no annotation coverage.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence with zero wasted words. It's front-loaded and appropriately sized for a simple tool, making it easy to parse quickly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the lack of annotations and output schema, the description is incomplete. It doesn't explain what 'label values' are in this context (e.g., metric label values in Prometheus), the return format, or error conditions. For a tool with no structured metadata, this leaves significant gaps.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema description coverage is 100%, with the single parameter 'labelName' documented as 'Label name to get values for'. The description adds no additional meaning beyond this, such as examples or constraints (e.g., label names must exist). Baseline 3 is appropriate when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description 'Get label values for a label name' clearly states the verb ('Get') and resource ('label values'), making the purpose understandable. However, it doesn't differentiate this tool from its siblings like 'get-series' or 'get-metadata', which might also involve label-related operations in a Prometheus context.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention context (e.g., for querying Prometheus metrics), prerequisites, or exclusions, leaving the agent to infer usage from the tool name alone among multiple sibling tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.