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

The description goes beyond annotations by disclosing payment requirements ($0.01/call, payment method, and 402 response without payment). This adds important behavioral context that annotations do not cover. No contradictions with annotations (readOnlyHint, idempotentHint, destructiveHint are consistent).

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 concise, with the main action front-loaded. Every sentence adds value: purpose, usage guidance, payment info, and return format. 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?

Given the tool's simplicity (2 parameters, no output schema), the description is complete. It covers purpose, usage, payment, and return fields. It also differentiates from sibling tools effectively.

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 the baseline is 3. The description adds value by providing example UN/LOCODE values and clarifying that the x_payment parameter is for payment proof, enhancing understanding beyond the schema alone.

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 clearly states the tool's purpose: look up port details by UN/LOCODE, including specific fields like name, country, coordinates, timezone, and facilities. It distinguishes itself from sibling shippingrates_search by advising to use that tool if the code is unknown.

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 explicitly tells when to use this tool (validate port codes, get port metadata) and when not to (if UN/LOCODE is unknown, use shippingrates_search first). This provides clear context and alternative guidance.

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