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

With no annotations, the description carries the full burden and does well: it discloses the $0.001 USDC cost, the x402 v2 payment requirement, and explicit non-goals (does not fetch the URL, sign payments, or settle independently). It stops short of describing what the inspected metadata actually contains, which matters most for a read-style tool.

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?

Front-loads the core action in the first sentence, then moves to cost and payment mechanics without padding. Four sentences each carry distinct information, though the payment-flow sentences are dense enough that the purpose statement could sit a bit more cleanly apart.

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?

There is no output schema and no annotations, so the description should explain the shape of the return value; 'response metadata' remains undefined (status code? headers? content type?). The payment and non-goal context is complete, but the agent cannot predict what it will receive from a successful call.

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?

Single parameter with 0% schema description coverage, so the description must compensate. It adds real constraints (the URL must be public and HTTP/HTTPS) and clarifies that the identical url argument must be repeated on the paid retry, but it gives no format examples or limits beyond the schema's maxLength of 2048.

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?

States a specific verb (Inspect) and resource (public HTTP/HTTPS URL response metadata), so an agent immediately knows it deals with URL metadata rather than the email-based siblings. It never names or contrasts itself with email_preflight/email_check_mini, but the resource difference is self-evident from the description.

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?

Explains the operational context clearly: unpaid calls return x402 v2 requirements, and a compatible client may retry with a signed PaymentPayload in params._meta. That tells the agent how the tool is expected to be invoked in a two-step payment flow, though it offers no explicit guidance on when to choose this over other tools or prerequisite conditions.

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