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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely non-annotated context: the answer is 'preliminary', it arrives with claim-level source IDs and review dates, and FAWs/rule evidence/all sources are omitted by default and must be opted into via include — that default-vs-optional behavior is exactly the kind of disclosure an agent needs.

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 purpose is front-loaded in the first clause, and the two short follow-on sentences handle input tolerance and the default/opt-in split. The middle enumeration of returned content is dense but every item is a distinct payload component, so it earns its place; only minor tightening is possible.

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?

There is no output schema, so the description must carry the return shape, and it does: claim-level source IDs, check_product-compatible facts, carrier context, review dates and cited sources. Together with the input tolerance note and the include opt-in, an agent has everything needed to call it and interpret the result.

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 a baseline of 3 applies, but the description adds meaning beyond the schema: it explains that slug tolerates slugs, named products and aliases (matching the schema's examples but framing the tolerance explicitly), and it characterizes include as an opt-in for material that is otherwise withheld, which the enum list alone does not convey.

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 opening clause gives a specific verb and resource with scope ('Get preliminary U.S. domestic shipping guidance for one product'), which is far more informative than the title alone. It also lists the return contents, so an agent knows what it gets. It stops short of explicitly contrasting itself with list_products or check_product, so it falls just below the top mark.

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?

Usage is implied rather than stated: the description says the response includes 'the facts check_product accepts', hinting at the get-then-check workflow, but never says when to call this versus list_products. The include clause does give actionable guidance on when to request extras ('left out unless requested with include'), which is real, if narrow, when-to-use advice.

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