billing_setDefaultPaymentMethodV1

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

No annotations are provided, so the description carries the full burden. It correctly indicates a mutating operation, but does not disclose details like reversibility, permission requirements, or side effects (e.g., what happens to the old default).

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 two sentences long, both relevant and concise. No redundant or unnecessary information.

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 simple, single-parameter tool, the description covers the basic purpose but lacks details on prerequisites, error conditions, or post-effects. Without an output schema, more context on expected behavior would be beneficial.

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 input schema describes the sole parameter 'paymentMethodId' as 'Payment method ID', and the description does not add further meaning. With 100% schema coverage, a baseline of 3 is appropriate.

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 clearly states the tool's purpose: 'Set the default payment method for your account.' It specifies the verb 'set' and the resource 'default payment method', making it distinct from sibling tools like billing_deletePaymentMethodV1 or billing_getPaymentMethodListV1.

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 description implies its use for configuring the primary payment method, but lacks explicit when-to-use or when-not-to-use guidance. However, the context of sibling tools (e.g., no other setter) makes the usage reasonably clear.

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