Prometheus: List Label Values

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

readOnlyHint=true already declares this a safe read, so the description's burden is lower. It adds no behavioral context beyond that — no note on result volume, the limit cap's effect, or what happens with a broad match — leaving only the schema to cover those.

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?

Two sentences with no filler; the operation and the optional selector scoping are front-loaded, and the second sentence earns its place by giving the concrete use case.

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?

For a read-only lookup tool with a fully described six-parameter schema and an obvious return shape (a list of label values), the description covers purpose, scoping and intended use. Only the return shape's ordering/truncation behavior is left unaddressed, which is minor.

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 100%, so start/end/limit/match/search are fully documented in the schema, which sets the baseline at 3. The description reinforces the selector concept with a deployment/pods example but adds no syntax or semantics not already present in the schema.

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?

States a specific verb and resource — listing the values a single label takes — with concrete examples (namespace, job, instance) that pin down what a 'label value' is. It implicitly separates itself from prometheus_list_labels (label names) and prometheus_list_metrics, though it never names the sibling it is not.

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?

Gives a clear situational cue: use it to resolve exact values before filtering, rather than guessing at a regex. That tells the agent when to prefer this over trial-and-error filtering, but there is no explicit contrast with prometheus_list_labels or prometheus_query.

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