list_payment_methods

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

With no annotations provided, the description carries the full behavioral burden and does declare 'Read-only', which is the key trait. It also explains the default-card fallback behavior. It does not cover auth requirements, rate limits, or pagination, but for a zero-parameter list tool this is solid coverage.

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?

Three short sentences, each earning its place. The core purpose and read-only nature are front-loaded, followed by the actionable follow-up step.

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?

An output schema already exists, so the description need not document return values, yet it still highlights the two fields that matter (id and default). Combined with the read-only declaration and sibling routing, nothing essential for correct invocation is missing.

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 no parameters, so the baseline is 4. The description's mention of a returned `id` is output-side information rather than parameter semantics, but it correctly connects the result to the set_payment_method workflow.

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 ('List the user's saved cards') and adds the distinguishing detail of surfacing the default card. It explicitly names the sibling set_payment_method, so an agent can tell this read/list tool apart from the setter without opening either schema.

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?

Explains the downstream workflow: take a returned `id` and pass it to set_payment_method, otherwise the account default card is charged. This gives clear context for when the tool matters, though there are no explicit exclusions or prerequisite conditions.

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