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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds rich behavioral context beyond that: the RRset comparison rules (order/case ignored, TXT case kept, TTLs ignored), the meaning of percentage as agreement not coverage, and the explicit 'Read-only HTTP, no auth, and no destructive actions'. No contradiction with annotations.

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 description is dense but every sentence carries necessary information: purpose, comparison semantics, defaults, return values, percentage caveat, usage guidance, and safety. It is front-loaded with the core purpose and uses no filler. The complexity of the tool justifies the length.

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 tool with no output schema, the description fully explains what is returned (every resolver response, queried/answered/failed counts, percentage). It also covers defaults, the caveat about agreement vs coverage, and the alternative tool. Nothing an agent needs to invoke it correctly is missing.

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 baseline is 3. The description mentions defaults for type and region, which are already in the schema. It does not add significant parameter-level meaning beyond what the schema provides, but it does not need to because the schema is thorough.

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: 'Compare DNS responses across the nine currently configured public and authoritative resolvers'. It states the purpose (detect propagation lag, missing answers, differing record sets) and distinguishes itself from siblings by emphasizing cross-resolver comparison. The explicit contrast with lookup_dns further clarifies its unique role.

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 description gives a clear when-to-use directive: 'Use when records were just changed and you suspect staleness'. It also names the alternative explicitly: 'for a single DNS-over-HTTPS lookup use lookup_dns instead'. This is exactly the kind of routing guidance an agent needs.

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