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

Annotations already declare readOnlyHint=true, openWorldHint=true, and non-idempotence, so the safety profile is covered. The description goes beyond by specifying the return shape (availability, price, sale_cost, checkout URL) and the 20-domain batch limit, which are useful behavioral facts. The closing 'Through Royally: its server marks it read-only' sentence is a redundant, somewhat confusing restatement of the annotation.

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?

Purpose is front-loaded, but the description is bloated: 'check up to 20', 'include_suggestions', and the multi-TLD list are each stated twice across the two paragraphs. The 'Through Royally' sentence adds no information beyond the annotations and reads like an artifact.

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?

No output schema exists, but the description compensates by describing exactly what each domain returns (availability, price, sale_cost, checkout URL) and how to present results. For a read-only search tool with full schema coverage, this is nearly enough; only the wpcom_site association behavior is left purely to the schema.

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%, so the baseline is 3. The description adds usage guidance for domains (creative candidates, multiple TLDs) and reiterates include_suggestions' effect, but repeats rather than deepens the schema semantics and gives no detail on wpcom_site or suggestions_count.

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+resource (search available domains, generate checkout links for registration on WordPress.com) with clear scope (up to 20 domains, any TLD). It implicitly clarifies that it does not complete the purchase ('a checkout URL the user can open to complete the purchase'), which resolves the tension with the 'purchase' in the name. It does not explicitly differentiate from the sibling wpcom-checkout-url tool.

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?

Rich when-to-use triggers: 'When a user mentions wanting a website, blog, online presence... proactively generate creative domain name candidates', plus the condition for include_suggestions (when domains are taken). However, it names no alternatives or exclusions (e.g., wpcom-checkout-url, wpcom-plans-list), so the guidance is clear on when to use but silent on when not to.

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