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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond that: it is a free public API, it fans out to roughly ten resolvers, and the result is a consensus comparison rather than a single answer.

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 with no filler: mechanism first, output second, use case last. Every sentence earns its place and the load-bearing detail is front-loaded.

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 two-parameter read-only query with a full output schema, the description covers mechanism, scope and purpose adequately, so return values need no explanation. It leaves minor gaps such as resolver locations or any rate limits implied by 'free public API', but nothing an agent needs to invoke it.

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% and both parameters (host, type with enum) are documented in the schema, so the baseline is 3. The description adds nothing about the host or record-type parameters beyond what the schema already states.

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 ('Query the same hostname across ~10 public DNS resolvers worldwide') plus the distinctive output ('report which ones return the same answer'). The multi-resolver scope implicitly distinguishes it from the single-lookup sibling tools_dns_record_lookup, though no sibling is named explicitly.

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?

'Useful right after a DNS change' gives a clear triggering context, which is more than most. However, it names no alternative (e.g. the single-resolver tools_dns_record_lookup or tools_cname_lookup) and states no when-not condition, leaving the agent to infer that this is the multi-resolver variant.

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