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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds real context beyond that: measures are kept separate by mode, output includes window totals, completeness, and percent change, and it guarantees it never fabricates a total across incompatible measures.

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: the first defines the output, the second defines the composition and metrics, the third gives usage triggers and boundaries. The core purpose is front-loaded with no 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?

With no output schema, the description carries return-value burden and does so reasonably (window totals, completeness, percent change, per-mode separation). Minor gaps remain on the exact shape of the pack and how prior-window defaults resolve, but nothing essential for correct invocation is missing.

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 description coverage is 100%, so the schema already documents port, response_format, and trailing_months with types, bounds, and defaults. The description adds no parameter-level detail (e.g., how trailing_months interacts with the current/prior windows), so the baseline 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?

States a specific verb (combine) and resource (every available official BTS crossing measure for one land-border port) and names the deliverable (a provenance-backed current-versus-prior activity evidence pack). The 'for one land-border port' scope and the aggregate-measures framing distinguish it from the sibling search/compare/trend tools without needing to name them.

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?

Gives explicit triggering examples ('build a border activity pack for Laredo', 'what changed at Otay Mesa?', logistics/corridor briefing) and a negative boundary ('not a congestion or wait-time measure'). It does not explicitly route to the sibling alternatives (bts_transport_search_ports, bts_transport_compare_ports, bts_transport_border_trend), so the when-not-this guidance is incomplete.

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