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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, so the safety profile is covered. The description adds behavioral context: it explains the shared rolling window, ranking by current count, and lists the return fields (prior-window count, completeness, percent change, exact window, stable port codes, provenance). It also explicitly states what it does not compare, clarifying scope beyond annotations.

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 deliver the core action, output composition, usage examples, and exclusions with no filler. Key information is front-loaded in the first sentence.

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?

With no output schema, the description compensates by enumerating the returned data: rankings, prior-window count, completeness, percent change, exact window, port codes, and provenance. It also gives concrete usage examples and exclusions, making the tool's behavior predictable. Given its read-only, idempotent nature and five well-described parameters, the description is complete enough for an agent to call 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?

Schema descriptions cover all 5 parameters at 100%, so the baseline is 3. The description adds context about the comparison window and measures ('one consistent official BTS crossing measure', 'shared rolling window') that maps to the measure and trailing_months parameters, but it doesn't add syntax or format details beyond the schema. Thus it remains at baseline.

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 a specific verb and resource: 'Compare two to eight U.S. land-border ports on one consistent official BTS crossing measure over a shared rolling window.' It also differentiates itself by stating what it does not compare (wait times, outbound flows, cargo value), making its purpose unambiguous relative to sibling tools.

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 explicit use-case examples ('Use this for compare truck crossings at Laredo, El Paso, and Otay Mesa') and a negative constraint ('It does not compare wait times, outbound flows, or cargo value'). While it does not name sibling tools, the examples and exclusions give clear guidance on when to select this tool.

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