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

Annotations already declare read-only and open-world behavior, but the description adds genuinely non-derivable context: a per-call price ($0.002 USDC), the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged. It still omits things like rate limits or payment setup prerequisites, so it falls short of a 5.

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 is front-loaded ('Mail and DNS hygiene of a domain over DNS over HTTPS'), followed by a dense but purposeful capability list and a single closing cost sentence. No filler; every clause 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?

An output schema exists, so return-value explanation is unnecessary, and annotations cover the safety profile. The description supplies capability scope, cost, and payment terms, leaving only minor gaps like latency or rate-limit expectations.

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?

Only one parameter, and schema description coverage is 100% ('Domain or URL, e.g. example.com'), so the schema fully documents it. The description adds no format or normalization detail (e.g. whether URLs are stripped), matching the baseline 3 for high-coverage schemas.

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 resource (a domain) and enumerates exactly what is checked: A/AAAA/MX/NS/TXT/CAA records, SPF, DMARC, DKIM, MTA-STS, TLS-RPT, BIMI, plus an issues list and letter grade. It does not, however, differentiate itself from close siblings such as `domain` or `email_check`, so an agent cannot tell them apart from the text alone.

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?

Intended usage (inspect DNS and mail hygiene for a domain) is strongly implied by the content list, but there is no explicit when-to-use, when-not-to-use, or named alternative among the many domain/email siblings. The agent must infer selection.

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