x402_pay_for_resource

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 states the main behavior but lacks details on failure modes (e.g., what if price exceeds max_price?), network errors, or whether the operation is destructive (deducts USDC). The description does not disclose error handling or side effects beyond payment.

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?

Single sentence, front-loaded with the action verb 'Fetch'. No wasted words; each part clarifies the tool's core function.

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 three parameters and no output schema or annotations, the description is somewhat complete for a simple fetch-and-pay tool. However, it lacks return value specification, error behavior, and clarification on what happens when price exceeds max_price, which is critical for a payment operation.

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 coverage is 100%, so the schema already documents all parameters. The description adds context ('automatically paying for it with USDC') but does not provide additional semantics beyond what the schema offers. Baseline 3 applies.

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 fetches an x402-protected URL and automatically pays with USDC if the price is within max_price. It uses specific verbs ('fetch', 'pay') and identifies the resource, distinguishing it from sibling tools like send_usdc (which only sends USDC) or conditional_payment.

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 usage when accessing x402-protected resources, but does not explicitly state when to use versus alternatives, nor does it provide when-not-to-use guidance or mention prerequisites. Sibling tools exist for payments, but no comparative context is given.

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