Purchase new domain

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

Annotations only say readOnlyHint=false and destructiveHint=false, so the description carries the behavioral burden. It discloses default payment method usage, default WHOIS fallback, TLD-dependent additional_details validation, and a concrete failure-handling step via hPanel. This goes well beyond the structured annotations.

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 description is a bit longer than the minimum but every sentence carries a practical caveat or prerequisite. It is front-loaded with the action. The final sentence 'Use this endpoint to register new domains for users' is slightly redundant with the first sentence, costing it a perfect score.

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?

The description accounts for payment defaults, WHOIS prerequisites, TLD-specific validation, and registration failure behavior. There is no output schema, and the description does not state what a successful response contains, which is a minor gap for a purchasing operation. Overall, it gives enough context for an agent to invoke the tool 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?

Schema coverage is 100%, so the baseline is 3. The description adds useful semantic context beyond the schema: payment_method_id defaults if omitted, domain_contacts defaults to TLD contact info, and additional_details may be required and validated. It does not add deep detail for item_id or coupons, but those are self-descriptive in the schema.

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 opens with a specific verb and resource: 'Purchase and register a new domain name.' It closes with a direct usage statement, 'Use this endpoint to register new domains for users,' which sharpens intent. This is clearly distinct from siblings like domain availability checks, transfers, or free-domain claims.

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 description gives clear context for using the tool: it is for registering new domains, requires WHOIS to exist for the TLD, and falls back to default payment/WHOIS when omitted. It does not explicitly name alternatives or state when NOT to use it, but the use-case guidance is strong enough for an agent to decide.

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