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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new information beyond those fields: it queries multiple servers worldwide and it costs 30 credits, which matters for invocation decisions. It stops short of describing throttling, result aggregation semantics, or caching, which keeps it from a 5.

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 opening redundantly restates the tool name twice before any substance ('DNS Propagation Checker: DNS Propagation Checker is a DNS checker API...'). The remaining sentences are efficient and the cost note is well placed, but the front-loaded duplication is wasted space in an otherwise short definition.

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 an output schema present and full schema coverage, the description does not need to explain return values. It supplies the purpose and the credit cost, which is the main missing piece for a paid API call. The one remaining gap is sibling differentiation against DNSLookup and DNSSECChecker.

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%, with both 'domain' and 'type' documented including a default of 'A' and examples. The description adds nothing about parameter meaning, so the baseline of 3 applies; the schema does all the work.

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: verifies whether DNS changes have propagated across multiple global DNS servers. An agent understands the operation, but the description never distinguishes it from close siblings such as DNSLookup, DNSSECChecker, or Nameservers that also query DNS records.

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 phrase 'verifies if DNS changes have propagated' implies the use case (after editing DNS records), which is helpful context. However, there is no explicit when-to-use or when-not-to-use statement, and no routing to alternatives like DNSLookup for a plain record fetch.

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