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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description adds real behavioral context beyond them: it discloses the return fields (status, answers, TTLs, observation time, DNSSEC flag), warns that it contacts an external resolver, and flags returned evidence as untrusted data rather than instructions. That trust-boundary note is material and not derivable from any structured field.

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?

Four compact sentences, all front-loaded: capability, return payload, side effect, then safety caveat. No filler and nothing repeated from the schema or annotations.

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 usefully enumerates the return fields and the external-contact side effect, and annotations cover safety. The remaining gaps are the unaddressed record-type parameter and the absence of any sibling routing, both of which an agent would want before calling.

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 only 50%: 'domain' is well documented in the schema, but 'type' carries an enum and default with no prose anywhere. The description says nothing about record type selection, the default of A, or valid domain formatting, so it does not compensate for the coverage gap.

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?

States a specific verb and resource ('Look up current public DNS records') and names the resolution path (Google Public DNS), so the capability is unambiguous. However, it never distinguishes itself from the sibling check_email_dns, which an agent must disambiguate between when the query is mailbox/domain-record related.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative sibling is named. The agent is left to infer that this is the general-purpose DNS tool versus check_email_dns or check_https, which is exactly the decision the description should settle.

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