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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description goes well beyond them: pricing ($0.001/call, 10 free/day, x402 payment-required result), error semantics (isError on invalid input or upstream failure, not charged), and the matching algorithm (longest match wins, Allow beats Disallow on ties, wildcards). That is exactly the extra behavioral context the annotations cannot express.

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 decision question, then a tight sequence of scope, matching rules, edge case, price, and error handling. Dense but every sentence carries operational information; nothing is redundant with the schema.

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?

An output schema exists, so return values need no explanation here. The description instead fills the remaining gaps an agent needs — pricing/payment path, failure behavior, and the robots.txt matching rules and missing-file default.

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%, so baseline is 3; the description adds meaning by clarifying that the URL is the one you intend to crawl and that rules are evaluated for any user-agent token, plus the wildcard/priority semantics that govern how the user_agent value is interpreted.

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 — checks a URL against robots.txt — and names the concrete outputs (sitemaps, crawl-delay, per-AI-crawler block status). This clearly distinguishes it from siblings like http_probe or web_meta, which cover reachability and page metadata rather than crawl policy.

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 opening 'May I crawl this?' frames the decision context well: use it before crawling a site. It gives clear conditions but does not name an alternative sibling or state exclusions (e.g. when to prefer http_probe or web_read instead).

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