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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered; the description adds real behavioral detail beyond that — data comes from a 'self-hosted snapshot', results are bounded and paginated, and each row carries a source hash and provenance for reproducibility. The most valuable addition is the unit caveat: counts are inbound crossing events, not unique vehicles or people, which prevents a common misinterpretation.

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, front-loaded with the core operation before the examples and the unit caveat. Every sentence contributes, though the example list is slightly long relative to the amount of new information it conveys.

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 the return-shape burden and does so: exact month, crossing count, stable port identity, pagination, source hash, provenance. Combined with the usage examples and the counting-semantics caveat, an agent has everything needed to call this 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 description coverage is 100%, including enum and format notes for measure, month patterns, and pagination bounds, so the schema does the heavy lifting and a 3 is the baseline. The description adds only the consistency constraint ('one consistent crossing measure') and the notion of a bounded window, which is marginally useful but largely restates the schema.

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 names a specific verb and resource ('Return a bounded monthly history for one official BTS land-border port and one consistent crossing measure') and scopes it tightly to a single port plus a single measure. That scoping implicitly contrasts with compare_ports and search_ports, but no sibling is named outright, so it stops short of a 5.

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?

It gives concrete invocation contexts ('monthly truck crossings at Laredo', 'pedestrian crossings at San Ysidro since 2023', a reproducible port-volume chart), which tells the agent when this tool fits. It never states when to prefer bts_transport_compare_ports or bts_transport_border_activity_pack instead, so there is context but no exclusions.

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