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

Annotations already cover the safety profile (readOnly, non-destructive, openWorld), and the description usefully adds the authentication prerequisite and where to obtain the key — exactly the kind of credential context that structured fields do not carry. It still omits rate limits or quota behavior for a keyed endpoint.

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?

Two tight sentences: the capability first, then the prerequisite in brackets. Zero filler and the most decision-relevant constraint 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 one-parameter read tool, the description covers what it returns (availability plus price) and the auth requirement, and no output schema exists to relieve it of more. The missing piece is routing relative to the public and bulk siblings.

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% and the single 'domain' parameter already includes a format example ('taskflow.app'), so the description adds no additional meaning such as TLD restrictions or normalization behavior. Baseline 3 applies when the schema does the heavy lifting.

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 ('Check if a domain is available') plus a secondary outcome ('get its price'). The '(signed in)' title and API-key note hint at the distinction from check_domain_public, but the description never names that sibling, so differentiation is only implicit.

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 bracketed API-key requirement implies this is the authenticated variant rather than the public check, but there is no explicit when-to-use guidance, no mention of check_domain_public or check_domains_public_bulk as alternatives, and no statement of when this tool should be preferred.

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