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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuine behavioral context by disclosing that the response is broad — a full write-up plus the entire ship fleet with page links — which warns the agent the payload is large. It does not mention not-found behavior for a bad slug/UUID, which is the main remaining gap.

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?

One dense sentence with the resource and identifier front-loaded, followed by the returned fields. It is efficient, though it reads as a fragment without an explicit verb and the field list is slightly comma-heavy.

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?

There is no output schema, so the description must carry return-value meaning — and it does, enumerating the fields and the nested fleet of ships. Combined with annotations covering the safety profile and a fully documented single parameter, an agent has everything needed to call it correctly.

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% and the single 'line' parameter is already documented as 'Slug (from list_cruise_lines) or UUID'. The description repeats the slug-or-UUID idea without adding format details, examples, or fallback behavior, 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?

Names the resource precisely ('One cruise line by slug or UUID') and enumerates the payload: owner, headquarters, loyalty program, website, write-up, and every ship in its fleet. That clearly separates it from list tools like list_cruise_lines. It stops short of naming get_cruise_ship or list_cruise_lines as the sibling it is not, so it is clear rather than explicitly differentiating.

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 only implied: 'by slug or UUID' signals a single-record lookup that requires an identifier, and the schema notes the slug comes from list_cruise_lines. There is no explicit statement of when to prefer this over get_cruise_ship (for a single vessel) or list_cruise_lines (for browsing all lines).

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