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

Beyond readOnlyHint/openWorldHint, it discloses a real operational constraint that annotations cannot convey: $0.002 USDC per successful call via x402 on Base, Solana or Arc, with failed calls not charged. That payment/auth detail is exactly the kind of context an agent needs before invoking. Pagination and volume per call remain unstated.

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?

Content scope is front-loaded, followed by filters and then price, which is a sensible order and contains no filler. The long field enumeration is somewhat redundant given an output schema exists, which keeps it short of a 5.

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 read-only data-retrieval tool with a full schema, output schema and annotations, the description covers dataset provenance (Tokyo MOU), temporal scope (one month per call, with defaults), filters and cost. Only volume/pagination expectations are absent, a minor gap.

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%, so all five parameters (imo, flag, port, year, month) are already documented in the schema. The description restates the three filters with the same examples (PA/LR/MH/TG) and adds no format or constraint detail beyond the schema, so baseline 3 applies.

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 precise verb+resource pair: 'Port state control detentions published by the Tokyo MOU (Asia-Pacific) for a month', and enumerates the returned fields. An agent can distinguish it from siblings like logistics_imo_vessel_dossier or logistics_sanctioned_vessel_check by the detention-specific scope, though no sibling is named explicitly.

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 states the available filters ('Filter by flag (2-letter code), IMO number or port') and that year/month default to last month, so usage is strongly implied. However, it never says when to prefer this tool over alternatives or what conditions make a lookup appropriate, leaving the agent to infer.

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