Set default payment method

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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the description is not burdened with the full safety profile. It adds modest behavioral context by noting the effect applies to future orders, but it does not disclose side effects such as overriding the current default or any required authentication.

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 only two sentences, with the core action front-loaded. The second sentence adds useful scope ('primary payment method for future orders') without significant filler.

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, non-destructive configuration endpoint with no output schema, the description is largely sufficient: it identifies what the call does and the effect. It could be more complete by explicitly noting that the current default is replaced and that the paymentMethodId must already exist on the account, but these are minor for such a simple tool.

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 description coverage is 100%, so the integer paymentMethodId parameter is already documented by the schema. The description adds no additional meaning about the parameter beyond 'payment method,' which aligns with the schema's baseline.

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 a specific action and resource: set the default payment method for the account. It makes the scope explicit with 'for your account' and 'for future orders,' though it does not contrast itself with sibling billing tools like billing_getPaymentMethodListV1 or billing_deletePaymentMethodV1.

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?

'Use this endpoint to configure the primary payment method for future orders' gives some context for when the setting applies, but it does not state when to choose this tool over alternatives or mention prerequisites such as a valid, existing payment method. The usage guidance is mostly implied rather than explicit.

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