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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety bar is met. The description adds genuinely new context: per-call pricing, a free sample invocation, the section-level return structure, and that data.errors names failed sections and data.billing reports what was delivered — useful partial-failure semantics absent from the structured fields.

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?

Front-loaded with the capability, followed by coverage list, price, sample, and return shape — every clause carries information an agent needs to decide and call. No filler or repetition.

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 present, the description steps in to describe the return envelope (data.sections.*, data.errors, data.billing) and the cost model. For a single-param read-only bundle, nothing needed to call 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 there is a single parameter, so the schema already documents 'domain'. The description reinforces the expected input format via the free sample {"domain": "example.com"}, matching the schema's bare-domain guidance without adding format subtleties.

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 resource and scope — 'Everything about a domain in one call' — then enumerates the exact sections bundled (DNS, WHOIS, TLS, DNSSEC, email auth, security score, blacklist, IP). The enumeration makes clear this is a bundle superset of the single-purpose siblings like domain_dns and domain_whois.

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 'one call' framing and the $0.025 price imply a cost/coverage tradeoff against the cheaper single-section siblings, but the description never explicitly says when to prefer this over domain_dns or domain_whois. Usage is implied rather than stated.

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