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

Adds substantial context beyond the annotations: AIS-derived source, non-VTS nature, transit-count-only limitation, real-time lag in the latest date, and precise pricing with failed calls uncharged. These are exactly the operational and cost traits an agent needs before invoking it.

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?

Front-loads the core purpose, then adds only high-value caveats and pricing. Two efficient sentences with no redundant restatement of the title or schema.

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?

Given annotations, a complete one-parameter schema, and an output schema, the description covers source, limitations, latency, and cost. 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 coverage is 100% for the single 'days' parameter, so the schema already documents its range and default. The description does not add further semantics about the parameter, which is acceptable but not enriching.

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 resource (daily vessel transits through the Malacca Strait chokepoint), count basis (by ship type with capacity), and source (IMF PortWatch, AIS-derived). The explicit 'Not VTS telemetry; transit counts only' also distinguishes it from vessel-level tracking 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?

Clearly establishes the applicable context and explicitly excludes VTS telemetry and vessel-level use. It does not name a specific sibling alternative, so it falls short of a full when/when-not/alternatives statement.

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