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

Goes well beyond the readOnlyHint/openWorldHint/idempotentHint annotations by disclosing that private addresses are refused, that AI-crawler robots.txt behavior and /llms.txt presence are probed, and that POST-body preservation across http-to-https redirects is tested. It also states the exact cost ($0.010 USDC on Base), the payment mechanism (x402 or credit token), and the free-credit fallback.

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 and client list are front-loaded in the first sentence, with secondary behaviors and payment details following. The nine-client parenthetical is long but each entry is informative rather than filler; overall it earns most of its length for a tool with this many facets.

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?

A read-only tool with an output schema and full annotation coverage needs no return-value documentation, and the description still explains what categories of findings appear and what it will not do (private addresses). Authentication/payment prerequisites are fully covered, so an agent has everything required to invoke it.

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 the schema already explains both url and credit_token, including the token's origin and purpose. The description only adds the pricing context around credit_token and the private-address restriction on url, which is useful but marginal against a fully documented 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 names a specific action (send one GET as each of nine named clients) and the exact resource (a URL), plus the concrete outputs it reports (refusals, robots.txt AI-crawler blocks, /llms.txt, POST-body redirect behavior). It does not, however, distinguish itself from siblings like reach_report, reach_report_rescan, or reach_report_status, so an agent must infer the difference between a one-off check and a persistent report.

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?

"Use before relying on a site or API from code, or to check your own" gives explicit context for when to call it, and the closing sentence routes to credits_trial when the caller lacks payment. No exclusion criteria or direct sibling comparison (e.g., when to prefer reach_report for ongoing monitoring) is provided.

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