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

Beyond the annotations (readOnlyHint=true, openWorldHint=true, destructiveHint=false), the description discloses that results are real-time, that creation and expiration dates come back for taken domains, that registrar and pricing details are gated behind paid plans, and that each call costs 10 credits. The credit cost and the tier-gated output are genuinely useful signals an agent cannot get from structured fields. It stops short of describing rate limits or failure modes.

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 content is front-loaded and the credit cost is a useful trailing note. But the opening redundantly restates the tool name and title ('Domain Availability: Domain Availability checks...'), wasting the most prominent position on repetition rather than new information.

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?

An output schema exists, so return values need not be spelled out in prose. The description still covers the meaningful result variations (availability status, dates for taken domains, plan-gated registrar and pricing data), making the definition complete enough to call correctly. Only the lack of sibling differentiation and input-format clarity keeps it from being fully complete.

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 with 100% schema description coverage, so the schema already fully documents it. The description adds nothing about the domain parameter's syntax or accepted formats (for example, whether a URL or a bare hostname is expected). Baseline 3 is appropriate when the schema does 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: 'checks domain availability in real time to show if a web address is open for registration or already taken.' That is concrete and actionable. However, it does not distinguish itself from closely related siblings such as DomainExpiration, DomainAge, WHOISLookup, or PhishingDomainChecker, even though it overlaps with them by returning creation/expiration dates.

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?

Usage is only implied by the purpose statement (check whether a domain is registrable). There is no explicit when-to-use guidance, no statement of when to prefer DomainExpiration or WHOISLookup instead, and no prerequisites or limits described beyond the credit cost.

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