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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds the useful fact that these fields appear on the post-payment thank-you page, but says nothing about the shape of the returned list (field keys, labels, required vs optional), which is the behavior an agent actually 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?

A single well-formed sentence with the resource and its purpose front-loaded; no filler. It is arguably too terse given the missing return-shape detail, but nothing in it is wasted.

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, zero-required-parameter lookup with no output schema, the description tells the agent what it retrieves and why. The remaining gap is that it does not describe the structure of the returned field list, but the core need for calling the tool is covered.

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?

There is only one parameter and the schema documents it fully (100% coverage, enum of 18 languages with default). The description never mentions the lang parameter or what changing it affects, so it adds nothing over the schema — baseline 3 applies.

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 (lists) and resource (the fields the customer fills in on the thank-you page after payment), which is much more concrete than the tool name alone. It does not, however, contrast itself with the siblings (faq, get_isbn_offer, get_order_link), so an agent must infer that this is the post-payment form-field lookup.

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 clause 'so an agent can help prepare them in advance' implies the usage context (pre-payment preparation support), but there is no explicit when-to-use/when-not guidance and no mention of the sibling tools as alternatives. Usage is inferable rather than stated.

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