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 discloses that the tool is 'free of charge', does not require an API key, and returns specific fields as JSON. It also explains the intended use for signing authorization. While it does not explicitly state read-only semantics, the nature of the tool implies it, making this a solid disclosure.

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 three sentences long, front-loads the core action, and provides necessary context without fluff. Each sentence contributes value—purpose, target user, return content, and sequencing—making it highly efficient.

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?

Given that there are no parameters, an output schema exists (though not shown), and the description covers the tool's purpose, target user, return content, and usage sequencing, it is complete for an agent to use this tool correctly. Nothing essential 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?

There are zero parameters, so the description correctly omits any parameter details. The schema coverage is 100% by triviality, and the baseline for zero parameters is 4. The description adds no unnecessary parameter information, which 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 states a specific action ('Return the x402 payment requirements') and a specific context ('for one categorization call'), clearly identifying the tool's purpose. It references the sibling `categorize_product`, distinguishing itself as a prerequisite step, and implicitly separates from `list_stores` by focusing on payment details.

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?

It explicitly states the intended user ('an agent that holds no API key') and the usage sequence ('before calling `categorize_product`'). This provides clear, actionable guidance on when to use this tool and how it integrates into a workflow, with no ambiguity.

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