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

With no annotations, the description carries the burden and does add non-obvious behavior: a 10-token cost per call under Navo Tokens and the fact that an empty answer is free. That is genuinely useful pre-call information. It does not state error/failure behavior or explicitly confirm the operation is side-effect free, leaving a modest 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?

Three short sentences: purpose and ranking first, then the decision use case, then the cost caveat. Nothing is repeated and nothing is wasted.

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, fully documented read query with no output schema, the description supplies the essentials, including the return ordering. Slightly richer detail on what a result row contains would make it complete, but the ranking statement covers the main need.

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% — both parameters are documented with UN/LOCODE format and examples. The description's "origin→destination port pair" restates the schema rather than adding format rules or edge cases, 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 gives a specific verb and resource ("Compare ocean carriers") scoped to an origin→destination port pair, and states the ranking criteria (on-time reliability, transit time), which separates it from global siblings like carrier_league or carrier_reliability. It stops short of explicitly naming the closest alternative, find_best_sailings, so an agent must infer 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?

"Use this to decide which line to book" gives a clear decision context for invoking the tool. There are no explicit exclusions or named alternatives (e.g., when to prefer find_best_sailings or get_schedules), so guidance is contextual rather than complete.

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