list_labels

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

With no annotations, the description is responsible for all behavioral disclosure. It only states the return format (JSON array) and parameter roles, but lacks details on potential volume, side effects, read-only nature, or any rate limits.

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 extremely concise: one line for purpose, a list of two parameters, and a return type. No superfluous information, 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 low complexity (2 optional parameters, no required, output schema exists), the description covers the essential functionality. It could mention that omitting both parameters returns all labels or clarify the time range semantics, but it is generally complete.

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?

The description adds meaning to both parameters with brief explanations ('Optional start of the time range for label filtering.') that go beyond the schema which only provides names and types. However, it does not specify expected formats (e.g., RFC3339) or behavior when omitted.

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 first sentence 'List all metric label names available in Thanos' clearly states the verb (list), resource (metric label names), and scope (Thanos), distinguishing it from sibling tools like list_loki_labels which deal with Loki log labels.

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?

No guidance is provided on when to use this tool versus alternatives (e.g., list_loki_labels, list_series). There is no mention of when not to use it or what the prerequisites are.

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