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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint, but the description adds genuinely new behavior: what the response contains (per-resolver answers and TTLs, agreement flag, majority answer), the supported record types, and the cost model ($0.03/call, first 25 free, failed calls free, repeats charged). The only gap is that it does not explain why idempotentHint is false beyond the billing angle.

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 output contents and the when-to-use conditions are front-loaded in the first two sentences, and pricing is correctly relegated to the end. Slightly redundant phrasing ('Reads or computes only and changes nothing') repeats what the annotations already state.

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 only two parameters and no output schema, the agent needs to know what comes back and what it costs, and the description covers both (per-resolver answers, TTLs, agreement, majority answer, per-call price with free failures). Nothing required 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 coverage is 100%, and both parameters are already documented in the schema including the URL-host acceptance and the record-type list. The description restates the record types and gives a bare name example but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 gives a specific verb and resource (check whether a DNS change has propagated) and immediately pins down the mechanism: the same record queried at five named public resolvers. It also names the sibling dns_lookup as the single-lookup alternative, so an agent can distinguish the two without inspecting schemas.

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?

It states the concrete situations that call for this tool (old value still cached after a record change, hosting move, email setup) and explicitly routes one-off lookups to dns_lookup. A worked parameter example is included.

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