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

Goes well beyond readOnlyHint/openWorldHint by naming both upstream sources per field group and warning that owner and class data may be years old — a real data-freshness caveat. It also discloses the commercial model: $0.002 USDC per successful call via x402 on Base/Solana/Arc, with failed calls free, which materially affects an agent's willingness to retry.

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?

Leads with the verb and key, then field coverage, then caveats and price — the important constraints are front-loaded and no sentence is filler. The field list is long but functions as scope-setting rather than padding.

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 one-parameter read with full schema coverage, an output schema, and readOnly annotations, the description supplies everything else an agent needs: sourcing per field, staleness risk, and per-call pricing with the failure-charge rule. Nothing material is left unstated.

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% and the single parameter already documents the 7-digit format with an example, so the description adds nothing new beyond 'by IMO number.' Baseline 3 is appropriate; the field enumeration describes outputs, not the parameter.

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 lookup: ship particulars keyed by IMO number, and enumerates the returned fields plus their two upstream sources. It is clear this is an identity/particulars lookup rather than a position feed, though it never names logistics_vessel_tracker or logistics_sanctioned_vessel_check to sharpen the boundary.

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?

Usage is implied by the required IMO key and the enumeration of described fields; an agent can infer 'call this when you have an IMO and need registry particulars.' But there is no explicit when-not guidance, no mention of what to do when the IMO is unknown, and no routing to the sibling tools that also accept vessels.

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