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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, yet the description still adds real behavior: the cost model (one shipping charge plus one customs fee per parcel, weight limit per parcel), the currency and duty inclusion, and the 'estimate, not a confirmed price' caveat. The main unaddressed edge case is what happens when a single item exceeds the per-parcel weight limit, and part of the return-value text overlaps the output schema.

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 Use when / Do NOT use / Returns ordering is strongly front-loaded and each block is one tight sentence. The three-language example block is longer than necessary for conveying intent, but it does demonstrate multilingual query support, so it earns partial keep.

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?

With an output schema present, the description needn't enumerate return fields, and it correctly focuses on triggers, exclusions and the pricing model. The only material omission for an agent to call it confidently is guidance on items that individually exceed a parcel's weight limit.

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 only 33%, so the description needs to carry meaning for items, ship_region and ship_country. It reinforces the country scope ('US, CA or JP') and the one-parcel-per-set baseline used for the saving figure, but it never explains the items array shape (bundle_sku/quantity) or the province-level tax effect beyond what ship_region's schema text already says — it mostly restates rather than compensates.

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 states a specific verb and resource — splitting the given sets into the parcels with the lowest estimated delivered total — and names both siblings it is not (estimate_total, request_quote). An agent can distinguish it from estimate_total and request_quote 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?

It gives an explicit trigger ('estimate_total says the parcel is over the weight limit, or the user asks how to ship many sets most cheaply') and explicit exclusions with the alternative named ('Do NOT use: for a single set in one parcel (estimate_total is enough), or to send a request (use request_quote)'). Both directions of routing are covered.

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