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

Beyond the annotations (readOnlyHint, idempotentHint, etc.), the description adds meaningful behavioral context: it is free, requires no auth, has no spend, and strictly confirms settlement without checking delivery or counterparty. This distinguishes the tool's behavior and limitations clearly.

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 concise (three sentences) and front-loaded with the core purpose. Every sentence contributes information about scope, constraints, or limitations; there is no redundancy or filler.

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?

The description provides strong context about inputs and limitations, but with no output schema, it does not explicitly describe what the tool returns (e.g., a boolean or structured confirmation). Given the tool's simplicity, this is a minor gap; the overall context is sufficient for most agents to invoke it correctly.

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?

While schema coverage is 100%, the description adds a cross-parameter constraint: 'an amount must be accompanied by a payTo or payer'. It also clarifies the matching semantics in the schema, such as 'matched as >=', which improves parameter understanding beyond individual field descriptions.

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 verb + resource: 'check that a Base-mainnet USDC transfer settled on-chain for a transaction hash', with optional matching criteria. It clearly distinguishes from siblings by scoping to USDC-settled x402 payments on Base and explicitly excluding non-USDC assets and service-delivery verification.

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 gives clear when-to-use context: 'Works for any USDC-settled x402 payment on Base — yours or one you received — not just Agoragentic invocations'. It also states what it does not do ('does not verify service delivery, output quality, or counterparty identity'), implying when not to use it, though it does not name a specific alternative tool.

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