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

Annotations declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), so the description need not restate it. The description adds a real behavioral detail not present anywhere else: it returns null for unknown multi-year term totals, which matters since there is no output schema.

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 short sentences, front-loaded with the core purpose, then the null-return caveat, then the exclusion. No padding or restatement of the title.

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 read-style estimation tool with full schema coverage and no output schema, the description covers purpose, scope, exclusions, and the null edge case. It could say more about what the estimate includes (currency, breakdown by year), but nothing essential for invocation 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 description coverage is 100%, so every parameter is already documented in the schema. The description adds only the general framing of 'one TLD at a registrar' and does not supplement the years, name, or registrar semantics, so baseline 3 applies.

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 with scope: 'Estimate new registration plus subsequent renewals for one TLD at a registrar.' It explicitly carves out what it is not ('Not a transfer or existing-domain renewal quote'), which separates it from pricing/link siblings.

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 gives clear when-not guidance for transfer and existing-domain renewal scenarios, which is genuinely useful routing information. It stops short of naming a specific alternative tool (e.g., get_tld_prices or search_prices), so the agent must infer the counterpart itself.

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