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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds crucial behavioral context beyond that: missing cutoffs remain null/absent and are not inferred, and the payment requirement (PAID: $0.03/call via x402, 402 if not paid) is disclosed. This is significant for an agent to avoid failed calls.

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 well-structured and front-loaded: first sentence states the core function, second gives usage context, third explains missing data behavior, fourth provides an alternative tool, fifth covers payment, and sixth summarizes the return structure. Every sentence adds essential information with no fluff.

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?

Despite having no output schema, the description includes a sample return structure ('Returns: { origin, destination, options: Array<{...}>, coverage }'), which is highly informative. It also covers payment prerequisites, data-fidelity expectations, and a clear alternative, making the description comprehensive for a 6-parameter tool.

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% (all parameters have descriptions in the schema), so the baseline is 3. The description adds no parameter-level details beyond what the schema already provides, but it does mention origin/destination in the opening sentence. It does not harm or add extra meaning to param usage.

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 opens with a specific verb ('Get') and a clear resource ('carrier vessel/voyage schedule options between an origin and destination') that includes cutoff deadlines. It explicitly distinguishes itself from the sibling 'shippingrates_vessel_schedule' by mentioning cutoffs, making the tool's purpose unambiguous.

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?

The description states exactly when to use this tool ('Use this for booking planning questions that need vessel details, voyage number, transshipment ports, ETA/ETD, and port/SI/VGM cutoffs') and provides a direct alternative: 'For port-call monitoring without cutoff details, use shippingrates_vessel_schedule.' This is explicit and actionable.

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