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

Beyond the read-only/open-world annotations, the description discloses important behavior: pricing at $0.002 USDC per successful call, x402 payment rails, failed calls not charged, and the critical caveat that an empty result is not a clearance. This is substantial operational and interpretive context.

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?

The description is front-loaded with the core action and packed with useful scope, output, and billing details. It is dense but nearly every clause earns its place; the single long main sentence is slightly heavy but not wasteful.

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 the output schema exists, the description still usefully summarizes returned fields and adds key limitations plus payment behavior. An agent has enough context to decide when to call it and what an empty result means.

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?

The input schema already fully documents both parameters, including vessel name length and IMO digit format. The description reinforces that the query can be by name or IMO number, but adds no format or edge-case detail beyond the schema; this matches the baseline for 100% schema coverage.

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 uses a specific verb and resource: searching the US OFAC SDN list for vessels by name or IMO number and returning matching vessel entries. It also states the scope boundary (OFAC SDN only, not UN/EU/UK lists), which helps distinguish it from broader vessel or sanctions-related siblings.

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 gives clear usage context: use the OFAC SDN list, not other sanctions lists, and an empty result is not a clearance. It does not explicitly name an alternative sibling tool for broader sanctions screening, which keeps it below a 5.

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