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

The description discloses output behavior—per-registrar registration/renewal/transfer prices, premium status, and a 2-year cost recommendation—which is valuable because there is no output schema. It also says 'live' and 'across registrars,' indicating external network queries; annotations already cover read-only/idempotent/destructive safety. The 10-minute cache default is only in the `fresh` parameter schema, but this is not a contradiction.

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 single sentence with no wasted words. It front-loads the scope and action, then packs in return contents and the recommendation basis without filler.

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 two-parameter tool with no output schema, the description covers the required input domain shape, the optional freshness behavior via the schema, and the return content in prose. Nothing required for invoking the tool correctly is missing.

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%, with clear descriptions for `domain` and `fresh`. The main description reinforces the 'one exact domain' idea and gives an example, but it adds no new parameter semantics beyond what the schema already provides. Baseline 3 is appropriate.

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 action—live availability and price comparison—for a specific resource: one exact domain across registrars. The 'one exact domain' scope clearly separates it from siblings like check_name_across_tlds or compare_tld_prices without needing their schemas.

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?

It clearly scopes use to a single exact domain rather than name exploration or TLD comparison, which is the main decision point among siblings. It doesn't explicitly name alternatives or say when not to use it, so it provides clear context but not full routing guidance.

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