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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description correctly spends its words on additive context: the external dependency on Google Public DNS and the warning that returned evidence is untrusted data rather than instructions. That prompt-injection caveat and the explicit limits of what is returned ('observations and DNS status, not deliverability or full policy validation') are genuine disclosure. It stops short of mentioning rate limits, caching, or lookup-failure behavior.

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?

Three short sentences, front-loaded with what is inspected, followed by scope limits, the external service, and the trust caveat. Every sentence carries distinct information and none is redundant with the name or schema.

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?

With no output schema, the description carries the burden of describing returns, and it does so adequately ('record observations and DNS status') while explicitly ruling out deliverability and full policy validation. It is largely complete for a single-parameter read tool; only operational details like failure modes or response shape specifics are absent.

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 documents the single 'domain' parameter, including the 'no URL, path, port or credentials' constraint. The description adds no syntax or format detail beyond that, so the baseline 3 for a fully documented schema is appropriate.

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 states a specific verb ('Inspect') and a precisely scoped resource (a public domain's MX, SPF and DMARC records), which is far more informative than a generic DNS check. It does not, however, name or differentiate itself from siblings such as lookup_dns or trace_email, so the agent must infer the boundary between this tool and a general DNS lookup.

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?

Usage is implied by the subject matter — check email-related DNS records for a domain — but there is no explicit when-to-use clause and no reference to alternatives like lookup_dns or trace_email. The 'not deliverability or full policy validation' line sets a boundary on interpretation, though it is framed as a caveat rather than selection guidance.

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