Get a TLD, or list them

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral context beyond those: the list is scoped to 'the TLDs this account can order' (narrowing the openWorldHint expectation) and warns that 'the full list is large', which informs agent pagination strategy. No contradiction with annotations.

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 zero filler: the first front-loads the primary get-by-id behavior and return contents, the second delivers usage guidance and a scale warning. Every clause earns its place, and the compact structure handles a dual-mode tool without redundancy.

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 dual-mode, 6-parameter read tool with pagination, the combination of the description, 100%-covered schema, output schema, and annotations is nearly complete: account scoping, large-list warning, and use-before-ordering guidance are all present. The one minor gap is that sort behavior is not tied to the list mode in the description, though the schema's sortField note covers it implicitly.

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%, and the schema descriptions are unusually rich (e.g., 'walk pages until a short one comes back', 'a wide page is truncated by the character limit'). The description reinforces id, tldName, and page usage but adds no meaning beyond the schema, so the 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?

The description uses specific verbs bound to a distinct resource: 'Returns one TLD by id with its registration terms, duration limits and registry-specific requirements, or lists the TLDs this account can order when id is omitted.' It fully disambiguates the dual-mode behavior and names concrete return contents, and the TLD resource is unique among all siblings, so it cannot be confused with eurodns_domain_get or eurodns_domain_check_availability.

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?

The description gives explicit when-to-use guidance: 'Check a TLD before ordering an unfamiliar extension', plus a concrete how-to-use recommendation to filter with tldName or page instead of requesting the full list. It does not name an alternative tool or state when-not-to-use, but no sibling covers TLD metadata, so exclusions are less critical.

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