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

With no annotations, the description must carry the burden of behavioral disclosure. It adds valuable context by stating the coverage is 'actually cached,' implying the tool reads cache state rather than computing theoretical ranges. It also discloses the specific field names and format. However, it doesn't address error handling or edge cases (e.g., invalid product codes), but for a simple read operation this is sufficient.

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 one sentence, front-loaded with the core action. It packs purpose, return format, and a usage hint into a single, well-structured line without any unnecessary words. The dash nicely separates the main behavior from the practical recommendation.

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 (one optional parameter, no nested objects, output schema present), the description fully covers the necessary context. It explains the tool's purpose, return values, and when to use it, including the consequence of not using it (empty window). There are no significant gaps for an agent to invoke it correctly.

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 input schema already provides 100% coverage of the single 'products' parameter with a clear description ('CN code(s) to check coverage for. Omit for the overall store range.'). The tool description adds no parameter-specific semantics beyond the schema, so the baseline of 3 applies.

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 a specific action: returning the period coverage (data_min/data_max) actually cached for given product codes. It includes the return format ('YYYY-MM') and explicitly distinguishes this as a data availability check, differentiating it from the many data-retrieval siblings.

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 gives explicit when-to-use guidance: 'use before picking period_start/period_end so you don't request an empty window.' This tells the agent exactly when to invoke this tool and provides a rationale. It effectively communicates the prerequisite context without needing to mention alternatives.

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