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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, but the description goes far beyond them: it discloses the live DNS-over-HTTPS transport, the Cloudflare/Google resolvers, the absence of WHOIS, the x402 payment requirement, the exact behavior of an unpaid call (returns PaymentRequired), and the retry mechanism via params._meta. This is exactly the kind of behavioral context annotations cannot convey.

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?

The definition is dense but front-loaded: the record list comes first, then transport and payment details. Every sentence carries information, though the single long sentence packs a lot and could be split for readability. No filler.

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 complex multi-check tool with no output schema, the description fully covers what is returned (including a plain-language issues list, status, final URL, HSTS, server) and how payment works. An agent has everything needed to call it correctly without opening anything else.

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 the schema already documents both parameters and the enum. The description adds only a mild restatement ('domain (or URL)' and 'https=0 skips the HTTPS GET'), which is redundant with the schema. Baseline 3 is appropriate when structured fields do the heavy lifting.

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 specific verb+resource ('One call for a domain (or URL)') and then enumerates exactly which records and checks are returned (A/AAAA, NS, SOA, MX, TXT, CAA, DNSSEC, SPF, DMARC, MTA-STS, HTTPS GET). This is far more specific than any sibling and lets an agent distinguish it from email_check or address_info immediately.

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?

It clearly states the use case ('One call for a domain') and a scoping exclusion ('No WHOIS'), plus an option to skip the HTTPS GET. It does not explicitly name alternative siblings or say when not to use it, so it falls short of the explicit when/when-not/alternatives bar.

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