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

With no annotations provided, the description carries full burden. It discloses the two-step payment flow, that results are dated crawl snapshots, and that the user is only charged when a result returns. This is substantial behavioral context, though it omits details like error handling, rate limits, or what happens if the resource is invalid.

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, each packed with essential information. It front-loads the cost and urgency ('BEFORE paying it'), then provides clear step-by-step instructions. There is minimal verbosity, but the density of information could be slightly overwhelming. Still, it 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?

Without an output schema, the description fills the gap by explaining the return value: an A–F grade and an 'accepts' array. It also covers the payment flow. While it does not detail error scenarios or edge cases, it provides sufficient context for a specialized vetting tool with moderate complexity.

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 description coverage is 100% (both parameters have descriptions in the schema). The description adds no new information about the parameters beyond what the schema already provides. It does clarify the two-step usage flow, but that is not parameter semantics per se. Baseline 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: 'Vet an x402 seller BEFORE paying it: A–F grade from observable signals'. It specifies the resource (x402 seller) and action (vet/grade), and distinguishes it from sibling tools like buy_api_key or get_x402_pricing by focusing on assessment before 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 provides explicit instructions: call once without x402_payment to get payment requirements, then call again with the payload. It also notes the cost ($0.02/call) and that charges only occur on result. However, it does not explicitly compare to sibling tools or state when not to use this tool.

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