byok-observability-mcp

prometheus_query

Execute PromQL queries to retrieve current metric values from Prometheus, enabling real-time monitoring of system performance and health.

Instructions

Execute an instant PromQL query and return the current value(s). Best for checking current state of a metric (e.g. CPU usage right now).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "query": "<query>"
    },
    "name": "prometheus_query"
  }
}

Input Schema

Name	Required	Description	Default
`query`	Yes	The PromQL expression to evaluate.
`time`	No	Evaluation timestamp as RFC3339 or Unix timestamp. Defaults to current time.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Apr 13, 2026

TDQS

A4.1/5.0

Behavior3/5

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 explains this is an instant query (not a range query) and returns current values, which is useful context. However, it doesn't mention authentication requirements, rate limits, error behavior, or what format the results come in (though the lack of output schema means this information would be helpful).

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 perfectly concise with two sentences that each earn their place. The first sentence states the core functionality, and the second provides crucial usage guidance with a helpful example. No wasted words.

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

Completeness3/5

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

For a query tool with 2 parameters (100% schema coverage) but no annotations and no output schema, the description provides adequate purpose and usage guidance. However, it lacks information about authentication, error handling, or result format that would be helpful given the absence of output schema and annotations.

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?

Schema description coverage is 100%, so the schema already fully documents both parameters. The description doesn't add any additional parameter semantics beyond what's in the schema descriptions. The baseline of 3 is appropriate when the schema does all the parameter documentation work.

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

Purpose5/5

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

The description clearly states the specific action ('Execute an instant PromQL query'), the resource ('current value(s)'), and distinguishes it from sibling tools by specifying it's for 'current state' checking rather than range queries or other Prometheus operations like health checks or listing metrics.

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

Usage Guidelines5/5

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

The description explicitly states when to use this tool ('Best for checking current state of a metric') and provides a concrete example ('e.g. CPU usage right now'), which implicitly distinguishes it from the sibling 'prometheus_query_range' tool that would be used for time-range queries.

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