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

Annotations already cover the safety profile (readOnly, destructive=false), and the description usefully reinforces that nothing is mutated while adding cost behavior not present in annotations: $0.01/call via x402 or credits, first 25 free, failed calls free, repeats charged. That cost/repeat note also explains the idempotentHint=false in practical terms. It stops short of stating rate limits or latency/timeout behavior, which for a five-resolver fan-out would be the one remaining operational unknown.

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 capability and resolver list are front-loaded, and the single dense paragraph covers purpose, alternatives, example and pricing without filler. The pricing clause is stated twice in slightly different forms ("first 25 free; failed calls free" then "each call is charged, so repeats are not free"), a minor redundancy in an otherwise efficient block.

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?

There is no output schema, yet the description compensates by enumerating what comes back: each resolver's answers and TTLs, whether they all agree, and the majority answer. Combined with the alternative routing to dns_lookup and the cost model, an agent has everything needed to call it and interpret the result.

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 coverage is 100%, so both parameters (name, type) are already fully documented, including the URL-host fallback and the A default. The description restates the record-type set and gives a name example, adding only marginal value over the schema. Baseline 3 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?

States a specific verb and resource ("Check whether a DNS change has propagated") and immediately names the exact mechanism: the same record queried at five named public resolvers, with agreement and majority answer. It also enumerates supported record types, so the scope is unambiguous against any sibling.

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?

Gives concrete triggering scenarios (old value still cached after a change, moving hosting, setting up email) and an explicit exclusion with the alternative: "for one lookup use dns_lookup." Nothing about when to pick this over dns_lookup is left to inference.

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