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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds a lot of information the agent could not otherwise know: 0.01 USDC pricing via x402, no account or API key, invalid input refused before payment, failed runs never charged, and an x402 PaymentRequired response without payment. Nothing here contradicts the read-only annotations.

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 capability summary, then payment terms and the sample/HTTP pointers in a logical order. It is dense and packs pricing, sampling and transport into one paragraph, but each element carries information an agent needs.

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 single-parameter read-only tool with no output schema, the description covers what comes back (scored report with every issue and its fix), what it costs, how payment works, and how to preview results for free. Nothing an agent needs to call it correctly is missing.

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 the schema itself documents that a URL or email is also accepted, so the description need not repeat it. The description adds no syntax or format detail for the single domain parameter beyond the HTTP example URL, so baseline 3 applies.

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?

Opens with a specific verb+resource ('Domain intelligence in one call') and enumerates exactly what is covered: DNS records, email security stack, RDAP registration data, and TLS certificate, plus a 0-100 score. An agent can distinguish it from site_audit, url_safety_check or company_enrich without opening any schema.

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?

Gives concrete use cases ('vetting a vendor, a sender or a lead') and points to get_example for a free sample before committing money. It does not explicitly name when to prefer a sibling such as url_safety_check or site_audit, so it stops short of full routing guidance.

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