list_payment_methods

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

Annotations already indicate readOnlyHint=true and destructiveHint=false, so the safety profile is clear. The description adds valuable behavioral context: it only returns cards, not other payment methods, and describes how to interpret an empty list. No contradiction with annotations.

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 concise sentences, front-loaded with the core purpose. The second sentence adds a critical caveat and alternative action. No wasted words. Every sentence earns its place.

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 list tool with one parameter and no output schema, the description provides all necessary context: what is listed (cards, default), what is not (other payment methods), and how to interpret an empty result. Fully adequate with annotations and schema.

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 has one parameter 'intent' with 100% coverage (description in schema). The tool description does not mention or supplement this parameter, so it adds no additional semantic value beyond the schema. Baseline score 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 lists saved cards and identifies the default. It explicitly warns that only cards are included, not wallets/gift cards, and advises against concluding 'no payment method' from an empty list. This provides specific verb+resource and distinguishes the tool's scope from potential alternatives.

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 not only says when to use the tool (to get saved cards and default) but also explicitly states when not to (do not conclude no payment method from an empty list) and suggests an alternative action (offer checkout-url instead). This provides clear and actionable guidance.

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