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

Annotations declare readOnlyHint and openWorldHint, but the description adds genuinely non-derivable traits: missing files are reported as absent rather than errors, the pricing model ($0.002 USDC via x402 across Base/Solana/Arc), and the guarantee that failed calls are not charged. This is exactly the context annotations cannot carry.

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?

Two sentences: the first front-loads purpose and output semantics, the second packs the absence-handling and pricing into one compact line. No waste, nothing buried.

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 an output schema present, return values need no explanation, and the description covers absence behavior and billing. Minor gap: no note on fetch timeouts, redirects, or rate limits for a live-fetch tool, but overall complete for correct invocation.

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% for the single 'domain' parameter, so the baseline applies. The description confirms it operates on a site's files but adds no format or edge-case detail (e.g., whether a scheme or subdomain is accepted) beyond the schema.

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 ('reads') against two named resources (robots.txt and security.txt), enumerates the content it extracts (crawl rules, sitemaps, RFC 9116 contact/expiry/policy), and describes the resulting verdict. An agent can distinguish this from the many search_* siblings at a glance.

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 purpose implies when to use it, but there is no explicit 'use when' or exclusion guidance, and no sibling alternative is named (e.g., relative to security_security_headers or security_whois_rdap). Implied usage only.

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