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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the cost model ($0.001 USDC via x402 on Base, first 5 calls/day free), the determinism guarantee (no AI), and the error semantics (4xx=allow all, 5xx=disallow all). It also states the exact matching rules, so the agent knows how results are derived rather than trusting a black box.

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?

Purpose is front-loaded, and the dense RFC parenthetical and price clause each carry information an agent needs. It is slightly clause-heavy but nothing is repeated or wasted.

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?

With no output schema, the description correctly enumerates the return payload (allowed, deciding rule and line, crawl-delay, sitemaps). Combined with pricing, error handling, and matching semantics, an agent has everything needed to decide to call it and interpret the result.

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 both parameter descriptions are adequate, so the baseline is 3. The description adds real value on top by explaining how user_agent is interpreted (group by product token else '*', longest match, Allow wins ties), which the schema's one-line description does not convey.

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 gives a specific verb and resource: it fetches robots.txt and evaluates a URL for a given user-agent token under RFC 9309. That is far more precise than a generic 'check' tool. It does not, however, explicitly distinguish itself from the sibling tools ai_crawler_access and sitemap_check, which an agent could plausibly confuse with this one.

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 'Crawl-permission preflight for agents and scrapers' makes the use context clear: run it before crawling a URL. It states no explicit exclusions or alternatives, so an agent must infer whether ai_crawler_access or sitemap_check is the better fit in a given situation.

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