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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that — prices are in AUD, there are exactly 11 products priced across 13 SKUs, and nothing is metered or subscribed — but the phrasing is metaphorical enough that details like currency semantics and result stability are only loosely communicated.

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 short and the core content (11 products, 13 AUD prices) lands early, but 'Included.' is a wasted opening fragment and 'The per-call doors stay open beside them' is decorative rather than informative. Every sentence should earn its place; here two sentences are mostly mood.

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 zero-parameter listing tool with no output schema, the description does sketch the record shape (products, prices, unit per payment, package return, input destination) and states the pricing model. What is missing is any note on whether the catalogue is static or live-fetched, but an agent can call this correctly from what is given.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate. It does describe what the catalogue entries contain ('the unit one payment buys for each SKU, what the package returns, and where the input is sent'), which maps to the returned fields rather than inputs.

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 conveys that this surfaces 'the one-off card packages as one machine-readable catalogue' with 11 products and 13 AUD prices, which is a recognizable resource. But it never uses a clear verb like 'list' or 'returns', opens with the opaque fragment 'Included.', and does not name the sibling buy_card_package, so the agent must infer that this is the read-side counterpart to purchasing.

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 per-call doors stay open beside them' gestures at alternatives (per-call tools vs. packages) but never states when to call this listing versus when to call buy_card_package or the per-call checkers. There is no explicit when-to-use or when-not-to-use guidance, only atmospheric hints.

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