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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description adds substantial value beyond them: enumerates returned fields, lists tracked registrars, and flags the important scoping caveat that prices are TLD standard, not premium names. That caveat prevents a common misinterpretation an agent could not infer from 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?

Three sentences, zero filler, and the usage trigger is front-loaded before the return-value detail. The final caveat sentence is short and earns its place.

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?

There is no output schema, so the description must describe return values — and it does so thoroughly (per-registrar pricing, cheapest buy, wholesale floor, renewal-trap flag, date-stamped). An agent has everything needed to call it and interpret results.

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% and the single `tlds` parameter is fully documented in-schema (with dot or without, max 20). The description adds no syntax or constraint detail beyond the schema, so baseline 3 applies.

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 (get TLD prices) and enumerates the exact data returned: first-year, renewal and transfer prices per registrar, cheapest buy, wholesale floor, renewal-trap flag. It is implicitly distinguishable from siblings (check_domain_availability, explain_tld) by its pricing focus, but never names an alternative 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?

The opening sentence gives concrete trigger conditions: 'when the user asks what a domain extension costs, where it is cheapest, or what it renews at.' That is a clear use context, though no when-not-to-use case or explicit sibling pointer is provided.

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