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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context beyond the annotations: the cost model (free within a daily allowance, then $0.002 USDC per call via x402) and the fact that results are rule-based with a trademark flag.

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 sentences, front-loaded with the deliverable and the strategies, followed by pricing. No filler, though the first sentence is dense with a comma-list that could be trimmed.

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?

With a full schema, an output schema, and annotations carrying the safety profile, the description need only add the cost/allowance model and generation scope, which it does. Nothing critical is missing for correct invocation.

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%, so the schema already documents all five parameters. The description references TLDs, prefixes, suffixes and the trademark flag, but adds no syntax, format, or defaulting detail beyond what the schema provides.

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 output (rule-based domain candidates) and enumerates the generation strategies (exact, stopword-free, hyphenated, prefixed, suffixed) plus the trademark flag, so an agent knows exactly what it produces. It implicitly separates itself from domains__availability (which would check a name), but never names or contrasts a sibling 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 implied by the description ('candidates for a keyword'), but there is no explicit when-to-use, when-not-to-use, or routing to alternatives such as domains__availability for checking live registration. The daily-allowance note gives context but not selection guidance.

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