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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, non-open-world), and the description adds genuinely useful behavior beyond them: the data is from licensed sources, AIS counts are unavailable with available=false and null counts, and the metric is vessels-present-in-radar-scenes over a 30-day rolling window versus a 2025 same-orbit baseline. It does not state auth requirements or rate limits, keeping it short of a 5.

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-loaded with the most decision-relevant fact (live counts unavailable) and compact at three sentences. The middle sentence is dense and slightly hard to parse ('carries Copernicus Sentinel-1 radar vessel presence (30-day rolling, % vs the 2025 same-orbit baseline)'), which costs it a point.

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?

For a no-argument read tool with no output schema, the description supplies the essentials: the null/available flag semantics and the definition of the one published metric. It leaves minor ambiguity about whether other chokepoints exist but are unpublished ('Where published...'), which keeps it just under complete.

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?

Zero parameters, so the baseline of 4 applies; there is no parameter surface for the description to clarify. No param-level information is needed or missing.

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?

Names a concrete resource (chokepoint vessel picture) and specifies the one populated dataset (Strait of Hormuz, Copernicus Sentinel-1 radar vessel presence). It is distinguishable from siblings like get_maritime_corridors, though the opening phrase 'chokepoint vessel picture' is loose and the negative framing ('live counts NOT available') competes with the actual purpose.

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?

The description signals a when-not condition ('Live AIS vessel counts are NOT available in this edition'), which steers the agent away from expecting live transit counts. However, it names no alternative tool and gives no positive guidance on when this tool is the right choice versus get_maritime_corridors or get_supply_chain_risk.

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