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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds useful behavior beyond that: what the values represent (one-year register/transfer/renew prices) and the practical consequence of omitting tlds (a very long result list).

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, zero filler. The output content is front-loaded and the parameter guidance follows immediately after.

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-only, two-parameter reference tool with no output schema, the description adequately conveys what is returned (per-extension register/transfer/renew prices and order links) and how to narrow results. It is complete enough to call correctly, though it says nothing about result size limits or pagination.

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%, so the baseline is 3. The description goes slightly beyond by giving a concrete tlds example (["com", "ca", "fr"]) and spelling out the default-when-omitted behavior, which the schema alone does not state.

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 (get prices) and resource (domain registration/transfer/renewal) with scope detail: one-year prices, per extension, plus order links. An agent can tell this apart from check_domain or compare_plans 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?

Clearly explains the condition that selects the broad vs narrow behavior: pass tlds for specific extensions, omit it to get all extensions (and it warns that this is a long list). It does not name alternatives like check_domain for availability, but the context of use is clear.

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