domain_subdomains

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

Annotations already declare readOnlyHint and non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that: an entire class of records (auto-created www-aliases) is silently excluded from this list and also absent from dns/getData — a gotcha an agent would otherwise misread as 'no such subdomain exists'.

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?

Purpose is front-loaded in one line, followed by the caveat and the fallback route. Every sentence carries information, though the parenthetical example (www.sub.site.ru → sub.site.ru) is slightly verbose.

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?

An output schema exists, so return values need no explanation. For a no-parameter read tool, the description supplies the one non-obvious fact (www-alias exclusion plus the dns_get fallback) that an agent cannot derive from schema or annotations.

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?

Zero parameters, so the baseline of 4 applies. There are no argument semantics to clarify, and the description correctly spends its budget on behavior instead of invented parameters.

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 first sentence names a specific resource and scope — all subdomains of the account — which implicitly separates it from domain_list (top-level domains) and domain_zones. It does not explicitly name a sibling, so it falls just short of a 5.

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 a concrete usage boundary: www-aliases are NOT returned here, and records for such names must be fetched via dns_get. That is explicit routing for an edge case, though it offers no general 'use this when…' framing versus other listing tools.

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