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

Beyond the read-only and idempotent annotations, the description discloses critical behavioral nuance: counts include only certified publishable dependencies, uncertified families report zero instead of falling back to legacy rows, and the countries/shipping_lines fields are distinct counts. Also notes the tool is free. This significantly enhances agent understanding of edge-case behavior.

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 compact and well-structured, with the main purpose in the first sentence, followed by usage context, behavioral details, the return shape, and related tools. Every sentence carries unique value, and there is no repetition or filler.

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 that there is no output schema, the description provides a full return structure with field names and type notation (ISO datetime). It also covers special fallback behavior, the FREE aspect, and direct pointers to related tools, making the description complete for an agent to invoke this tool without additional context.

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 tool has zero parameters, so the description cannot add parameter-specific meaning beyond the empty schema. The rubric sets a baseline of 4 for zero-parameter tools. The description does clarify the semantics of returned fields (e.g., distinct counts), which partially compensates for the lack of output schema, but since parameters are nonexistent, a perfect score is not warranted.

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 opens with 'Get current counts from ShippingRates customer-published datasets,' which clearly states the specific verb (get), resource (counts from datasets), and scope. It also explicitly differentiates from related tools by naming shippingrates_lines and shippingrates_search as alternatives, making the purpose unmistakable.

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 explicitly instructs 'Use this before calling data tools' and provides direct alternatives: 'Use shippingrates_lines for per-carrier breakdowns, shippingrates_search for keyword discovery.' This gives clear when-to-use and when-not-to-use guidance relative to siblings.

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