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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real behavioral value beyond them: the result ordering ('Ships on the map now come first') and the one-year recency window, neither of which appears in the annotations or schema. It stops short of describing the result envelope, but an output schema exists to carry that.

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?

Two sentences, front-loaded with the lookup capabilities and followed by the ordering rule and the escalation path. Nothing is repeated and no sentence could be removed without losing information.

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 two-parameter search with full schema coverage and an output schema, the description covers query formats, result ordering, scope limits, and the handoff to get_ship. An agent has everything needed to decide to call it and to interpret the ordering of results.

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%, so both parameters are documented in the schema, which sets the baseline at 3. The description earns above that by supplying the identifier formats — MMSI is 9 digits and IMO is 7 — that the schema leaves unspecified, letting the agent validate a query before calling.

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 specific verb (find) plus the resource (ships) and the exact identifier types accepted, including their digit lengths. It also scopes the searchable universe (any class, on the map now or heard in the last year), which no sibling shares.

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 explicitly routes to the alternative: 'Use get_ship with an MMSI for the whole record,' which tells the agent when this tool is sufficient and when it is not. The remaining siblings (search_ports, get_port) operate on a different resource, so no further exclusion is needed.

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