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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description correctly avoids contradicting them. It adds valuable behavior beyond annotations: payment requirement per call (USDC/USDT on Base via x402) and the 3-free-calls-per-wallet policy, plus what the parsed result will contain.

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 with no wasted words: the first states the core functionality and outputs, the second handles payment and free-tier details. Critical information is front-loaded, and supplementary cost details are placed at the end where they belong.

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?

For a read-only query tool with 5 parameters (1 required) and a rich output schema, the description covers the essential behavioral aspects—what it does, what it returns, and how billing/free tier works. It does not cover edge cases like timeouts or error handling, but these are minor gaps given the output schema and annotations.

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 description coverage is 100%, so each parameter (url, wallet, api_key, x_payment, user_agent) is already documented. The description adds only marginal parameter context by echoing the user-agent concept ('this user-agent') and clarifying that x_payment is the payment payload, but does not substantially enrich parameter semantics 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?

The description opens with a precise question it answers ('may this user-agent crawl this URL?') and names the exact mechanism (fetching and parsing robots.txt). It lists concrete outputs (allowed flag, crawl-delay, request-rate, sitemaps), which clearly differentiates it from siblings like url_status, seo_check, and web_crawl.

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 tool's intended use is made obvious by framing it as a yes/no question about crawl permission, giving an agent clear context for when to invoke it. However, it does not explicitly mention alternatives or exclusions, relying on the tool's distinct purpose to imply selection.

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