query_metrics

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

With no annotations, the description carries the full burden. It discloses return value structure ('JSON payload with resultType and result') and default behavior for time ('now when omitted'). It does not mention side effects or error conditions, but the read-only nature is implied. For a simple query tool, this is sufficient but not exhaustive.

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

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

The description is very concise, with a clear one-line summary followed by structured parameter explanations and return value description. Every sentence adds value, and the key information is front-loaded.

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

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

Given the tool's simplicity (2 parameters, no nested objects) and the presence of an output schema (though not detailed), the description covers core functionality. It explains the return JSON structure and parameter semantics. Minor omissions like error handling or rate limits are acceptable for a straightforward query tool.

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

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

Schema description coverage is 0%, but the description fully explains both parameters: query with a concrete PromQL example, time with explicit format options (RFC 3339 and Unix timestamps) and default behavior. This compensates completely for the missing schema descriptions.

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

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

The description clearly states 'Run an instant PromQL query against Thanos.' It specifies the verb (Run), the resource (PromQL query), and the scope (instant, as opposed to range queries). The differentiation from siblings like query_metrics_range and the Loki tools is implicit through the naming and context.

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

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

The description provides examples for both parameters (query and time) and explains optional timestamp formats. However, it does not explicitly state when to use this tool versus siblings like query_metrics_range or Loki tools. The guidance is adequate for parameter usage but could be improved with direct alternatives.

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