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

Goes well beyond the annotations by disclosing the cost model ($0.005/call, 25 free, failed calls free), the auth paths (x402 USDC or card key at /credits), and that repeat calls are charged — which operationally explains the idempotentHint=false flag. The 'reads or computes only and changes nothing' line reinforces rather than contradicts readOnlyHint=true.

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 list is front-loaded and each sentence carries information: capabilities, use cases, sibling routing, example, pricing. Minor redundancy in 'Reads or computes only and changes nothing,' which echoes readOnlyHint=true, but the density of the pricing/auth sentence justifies its 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?

With no output schema, the description compensates by enumerating the return contents (record types, policies, ages, mail acceptance). Combined with cost, auth, and failure behavior, an agent has everything needed to decide and call correctly.

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?

There is a single parameter and schema coverage is 100%, with an inline example in the schema itself, so the schema carries the full burden. The description's 'Example: name=cloudflare.com' merely restates what the schema already documents, adding no new format, normalization, or subdomain/IP-handling detail. 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 capability ('Domain intelligence in one call') and enumerates the exact record types and data classes returned: DNS records, DNSSEC status, registrar, registration/expiry dates with age, SPF/DMARC. It also explicitly contrasts itself with the sibling domain_report, so an agent can separate the two without opening a schema.

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?

Names concrete use cases (lead qualification, phishing/trust checks, deliverability audits) and routes to the alternative with an explicit condition: 'For a trust verdict with named flags use domain_report.' An input example is also provided, leaving nothing to inference.

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