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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that: it discloses ranking behavior, that a prior-window count and reported-month completeness are returned, and that port codes are stable and provenance is included — meaningful for a tool with no output schema.

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?

Three sentences, each earning its place: action and scope first, then returned fields, then usage examples and exclusions. Front-loaded and free of redundancy.

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 correctly compensates by enumerating the return contents (prior-window count, completeness, percent change, window, codes, provenance). Scope, usage, and exclusions are all present, leaving nothing essential missing for a correct call.

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 coverage is 100%, so the baseline is 3, and the schema already spells out the ports count bounds, the measure enum, and the trailing_months window. The description adds conceptual meaning beyond the schema by framing the window as a shared rolling current/prior comparison, tying trailing_months and end_month to a concrete comparison model.

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 (compare), resource (U.S. land-border ports), and scope (two to eight ports, one BTS measure, shared rolling window). Clear and unambiguous, but it never names its closest siblings (bts_transport_border_trend, bts_transport_search_ports), so sibling differentiation is left implicit.

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?

Provides two concrete invocation examples ('compare truck crossings at Laredo, El Paso, and Otay Mesa') and explicit exclusions ('does not compare wait times, outbound flows, or cargo value'). Strong when/when-not guidance, though it does not point to the alternative tool to use instead for those excluded cases.

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