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

Annotations already establish read-only, idempotent, closed-world safety, so the description's job is additive. It does that by disclosing a non-obvious behavior: it still answers for well-known non-existent TLDs like .eth or .web rather than erroring, and it reveals the content is an editorial/subjective verdict from tld.expert.

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, with the triggering user intents front-loaded before the return-value inventory. The parenthetical examples and the return list are dense but each earns its place by clarifying scope.

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, so the description must carry the return-value burden, and it does: verdict, pros/cons, registry, restrictions, use cases, typical price. The remaining gap is that editorial-verdict semantics (subjectivity, freshness) are only lightly implied.

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?

One parameter with 100% schema description coverage; the schema already documents that the TLD may be given with or without a leading dot. The description adds nothing further about the argument format, so 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?

Specific verb (explain) plus resource (TLD), and the description enumerates exactly what questions it answers: meaning, operator, registration eligibility, project fit. It is clearly distinguishable from siblings get_tld_prices, check_domain_availability, and suggest_tld_alternatives.

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?

Gives a concrete trigger condition and three example user utterances, which is strong 'when to use' guidance. It stops short of naming alternatives for overlapping questions (e.g., price lookup routes to get_tld_prices) since it advertises a typical price in its own output.

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