Checkout options: languages, currencies, payment methods

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is fully covered by structured data. The description's only behavior beyond that is the currency-to-payment-methods dependency and the enumeration of supported payment rails, which is genuinely useful but not accompanied by any note on fallback behavior for unsupported countries or precedence when both country and currency are supplied.

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?

Two sentences, front-loaded with the resource set before the behavioral detail, with no filler. The parenthetical list of payment rails is long but carries informational value; the only minor redundancy is restating the domain (simvito.com checkout) first stated in the title.

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 zero required parameters, an output schema, and full annotation coverage, the description does what is needed: it explains what is returned (default currency plus eligible payment methods) and the defaults applied. The missing piece is orchestration context — when in the checkout flow to call this before start_checkout.

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 the baseline is 3, but the description adds real meaning on top: it states that country drives the default currency, and that language determines how names and links are rendered — a downstream effect not captured in the schema's 'language of the conversation' wording. It also clarifies that currency governs which payment methods are payable.

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 names the concrete resource set (languages, currencies, payment methods at simvito.com checkout) and states the outcome of passing country or currency, so an agent knows it is a configuration/lookup tool rather than a transactional one. It does not explicitly contrast itself with start_checkout or get_buy_link, which sit closest to it in the sibling list.

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 only implied: 'Pass the buyer's country or currency to get the default currency there' suggests the tool is called ahead of presenting checkout, but there is no explicit when-to-use statement, no guidance on choosing between country and currency, and no mention of how it relates to start_checkout. The agent must infer the call site.

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