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

Annotations already declare readOnly, idempotent, openWorld, non-destructive. The description adds real value beyond them: data freshness ('refreshed daily'), source breadth (40+ registrars), currency and unit (USD per year), default sort rationale, and that offers link out to a purchase page.

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?

Three tight sentences, each carrying distinct information: scope/source/currency, sorting default plus the reason it matters, and the outbound buy links. Nothing is repeated from the schema and the rationale is front-loaded.

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?

For a read-only, open-world lookup with no output schema, the description adequately conveys what comes back (per-registrar offers with links) and the cost basis being compared. Only the sort options and result cap remain unspecified for an agent tuning the call.

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 only 33% – just the 'tld' param is documented, and the description usefully explains the default 'three_year' sort and the annual USD basis. But the other three enum values (registration, renewal, transfer) and the 'limit' param (default 10, max 60) get no semantic treatment in either place, so the low-coverage schema is not fully compensated.

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 states a specific resource and scope: every tracked registrar's price for one TLD, in USD per year, sourced from 40+ registrars, with buy links. That is far more concrete than the title and clearly separates it from temporal tools like price_history, though no sibling is named explicitly.

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 – the framing 'sorted by 3-year cost ... because a cheap first year often hides an expensive renewal' hints at the comparison use case, but there is no explicit when-to-use, no exclusion of price_history for historical data, and no prerequisites stated.

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