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

No annotations are supplied, so the description carries the full disclosure burden. It does useful work by promising per-check verdicts plus a 0-100 score, which reveals the response shape, but it says nothing about cost, latency (a ten-check audit is heavier than a single lookup), failure behavior for unresolvable domains, or whether the tool is strictly read-only.

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 purpose and the check inventory are front-loaded in one dense sentence, with the return value stated up front at the end. The long parenthetical enumerations are information-bearing rather than filler, though the RFC 7208 and aspf/adkim details sit close to noise for an agent deciding whether to call it.

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, single-parameter audit this covers purpose, scope, and the shape of the result well enough to call confidently. Remaining gaps are modest: no guidance on invalid/unresolvable domains, timing expectations, or how the 0-100 score is composed (though details are promised per-check).

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?

There is a single required parameter and schema coverage is 100%; the schema already explains that an email address is normalized to its domain. The description adds no further parameter meaning, 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?

The description opens with a specific verb and resource ("Full email-deliverability audit for a domain") and then enumerates the exact checks performed (MX, SPF, DMARC, DKIM selectors, rDNS, BIMI, MTA-STS). This unambiguous scope makes it easy to separate from single-purpose siblings such as check_mx, check_dkim, and check_dns.

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 word "Full" implicitly signals this is the comprehensive option versus the narrow per-record sibling checks, but the description never states when to prefer it over check_mx or check_dkim, nor any preconditions. Usage must be inferred rather than read.

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