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

The description goes beyond annotations by disclosing the source (self-hosted snapshot), the output contents (exact month, crossing count, stable port identity, pagination, source hash, provenance), and the counting semantics (inbound events). The annotations already establish read-only/idempotent/destructive false, and the description adds practical expectations without contradicting them.

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 – a precise purpose, a usage trigger phrase, and a clarification of the measure unit. All high-signal, no filler; the most important capabilities are front-loaded.

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?

The tool has 7 parameters and no output schema, but the description enumerates all key output fields (exact month, crossing count, stable port identity, pagination, source hash, provenance) and gives concrete invocation examples. It doesn't specify error/runtime behavior, but the annotations plus open-world hint make it sufficiently complete for an agent to invoke 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?

With 100% schema coverage, the schema already documents every parameter. The description adds contextual meaning: 'bounded monthly history' implies limit/offset behavior, and 'one consistent crossing measure' clarifies that measure parameters must not be combined. It doesn't repeat schema descriptions but gives agent interpretation guidance.

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 ('Return'), resource ('bounded monthly history'), and scope ('one port', 'one consistent crossing measure'), and clarifies the counting unit ('inbound crossing events, not unique vehicles or people'). The examples of Laredo and San Ysidro anchor it visually. It clearly differentiates from the sibling comparison/search/pack 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?

Explicitly tells the agent when to use it: monthly truck/pedestrian crossing queries and reproducible port-volume charts. It doesn't name sibling alternatives or exclusions, but the use cases are concrete and the scope constraints ('one port, one measure') imply it's not for comparisons (use compare_ports) or discovery (use search_ports).

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