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

Annotations already cover safety (readOnly, non-destructive, open-world), and the description adds real substance beyond them: the lookup hits the live registrar, is capped at 20 names, and returns per-name registrability, first-year and renewal price in USD, plus a failure reason. It does not mention latency, rate limits, or partial-failure behavior.

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, with the trigger condition front-loaded before the behavioral and routing details. Every sentence carries distinct 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?

No output schema exists, and the description compensates by spelling out the per-item return fields and the failure-reason case. The remaining gap is the unstated exclusivity between the single-domain and list-domain parameters, which an agent must guess at.

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 75%, giving a baseline of 3. The description does add the important combinatorial semantics that 'name' plus 'tlds' generates the candidate list versus passing exact domains, but it never clarifies whether 'domain' and 'domains' are mutually exclusive or how precedence works — the key ambiguity in this four-parameter, zero-required schema.

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 — checking domain name availability and price against a live registrar — with scope (up to 20 names, exact domains or name+endings). It also names the sibling screen_domains it is not, so an agent can separate the two without opening 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?

Explicit trigger ('when someone wants to know whether specific domain names can be registered and what they cost') plus a routing rule to use screen_domains first for many names. It does not contrast with suggest_domains or domain_info, so the alternative-space is only partly covered.

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