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

The description discloses exact cost ($0.01 USDC on Base), the payTo address, output-shape parity with check, and even the pricing of subsequent result fields. This goes well beyond the readOnlyHint and openWorldHint annotations and leaves little hidden about the paid batch behavior.

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 front-loaded with the most important facts: paid, batch, max 10 URLs. The parenthetical list of next.* prices adds detail useful for understanding responses but is somewhat noisy for selecting or invoking the tool.

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, but the description at least references the free check result shape and the has402 conditional field. It is largely complete for a one-parameter paid batch tool, though it does not define what an 'x402 honesty probe' actually returns beyond that shape.

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% and already documents the 1-10 URL array, SSRF-safe rules, and that payment headers are not sent to targets. The description adds pricing context but no additional per-parameter meaning beyond what the schema provides.

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 identifies the resource as a batch operation over up to 10 URLs and ties it to the free 'check' tool by saying each result has the same shape. It never explicitly states 'checks multiple URLs', relying somewhat on the tool name and sibling context, but it clearly distinguishes check_batch from the single-URL free check.

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 phrase 'GET /check stays free for one URL' provides a clear singleton-vs-batch heuristic, and the paid amount plus max-10 limit signal when this batch path is appropriate. It does not explicitly say 'use check for one URL and check_batch for multiple', but the implication is strong.

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