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

Annotations only declare readOnlyHint and openWorldHint, yet the description discloses the $0.001 USDC cost on Base, the x402 payment flow, and that unpaid calls return PaymentRequired with automatic payment by x402 clients. It also enumerates what the response contains, which goes well beyond structured metadata.

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-loaded with the core question and answer format, then payment details. Dense but every sentence carries information; the payment sentence is slightly long but justified for a paid 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, so the description must describe return values, and it does: allowed true/false, matching rule, sitemaps, and the 14 AI crawler checks. Combined with the payment behavior, an agent has everything needed to call 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?

Schema coverage is 50%: url is documented in the schema while userAgent has only a default and no description. The description mentions 'your user agent and path', giving partial context, but does not clarify the '*' default or how path is derived from the URL.

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 and resource ('parses robots.txt and answers allowed true/false') and frames the exact question an agent would ask ('May I crawl this URL?'). Clearly distinct from siblings like dns_lookup, url_check, and url_metadata.

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 framing 'May I crawl this URL?' makes the use context obvious, and the mention of user agent vs path clarifies scope. It does not explicitly name when to prefer a sibling or any exclusions, keeping it just under a 5.

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