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

Annotations already cover the safe-read profile (readOnlyHint=true, destructiveHint=false), so the description's added value is real: it discloses that rates vary with weight/size/ZIP/packaging and must be re-fetched, that nothing is purchased, and that a Cotlet API key with app access is required. No return format is given, but that is minor for a quote call.

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?

Front-loaded with the core purpose and appropriately short, but the second sentence ('Returns each service Pirate Ship offers for this package with its price') largely restates the first, which already said 'services with price'.

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 read-only quote tool with no output schema, the description covers purpose, the drivers that change results, the non-purchasing nature, and the auth requirement. Only an explicit routing to the buy tool is missing.

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%, so the schema already documents all five parameters, establishing a baseline of 3. The description reinforces which inputs drive pricing (weight, size, ZIP, packaging) but adds no format or syntax detail beyond the schema.

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?

States a specific verb+resource ('USPS and UPS services with price for one package, cheapest first') and its scope. The phrase 'for one package' implicitly distinguishes it from the sibling pirate-ship_get_batch_rates, so an agent can tell them apart without opening either schema.

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?

Gives clear context ('Nothing is bought') that frames this as a quoting step before a purchase, and instructs re-calling when weight/size/ZIP/packaging changes. It does not explicitly name buy_label as the alternative or state exclusions, so it falls short of a full when/when-not routing.

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