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

Annotations already cover the read-only, non-destructive, closed-world safety profile, so the description is additive by disclosing how different providers appear in the result: Stripe saved cards carry ids, Dintero/Vipps come back as payment types. That shape information matters for choosing the next call, though the phrase 'returned as payment types' is terse and not fully unambiguous.

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 compact sentences with the purpose front-loaded and the return-shape detail after it. No filler, though the second sentence is compressed enough that it borders on cryptic.

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 single-parameter read-only list with no output schema, the description covers purpose and partial return shape. Missing are edge behaviors such as an empty cart or uninitialized session, but nothing essential for a correct invocation is absent.

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?

Only one parameter exists and schema description coverage is 100%, so the schema fully documents storeId. The description adds nothing parameter-specific, which is acceptable at the baseline given the schema does the work.

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 and resource: lists payment methods available for the current cart/user. That is clearly distinct from the cart_* and checkout_* siblings, though the description does not explicitly name the alternative tools it should be paired with (e.g. checkout_start).

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 by 'for the current cart/user' – the agent can infer this is a pre-checkout discovery call, but nothing states when to call it versus checkout_start or what preconditions exist (empty cart, unauthenticated user). No exclusions or alternatives are named.

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