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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely useful behavior: a 50-name cap and the fact that overflow items are reported in the response rather than silently dropped. It still doesn't say what the result contains or how the check behaves, so it is useful but not rich.

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 tight sentences, front-loaded with the scope (batch, up to 50) before the when-to-use guidance and the overflow note. Almost no filler, though 'То же самое' spends the opening clause on a back-reference instead of stating the operation.

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 simple two-parameter read-only tool with no output schema, the description covers scope, limit, usage and overflow handling. The gap is that it never states what the check returns or what 'the same thing' refers to, leaving the core result semantics to inference from the sibling tool.

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%, with both `domains` and `only_available` documented in the input schema, so the baseline is 3. The description reinforces the 50-item limit and the overflow behavior but adds nothing about the filter parameter beyond the schema.

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 makes clear this is the batch form ('сразу для списка, до 50 имён за вызов') and contrasts it with one-by-one checking, which lets an agent distinguish it from the sibling check_domain. However, it never says what 'check' actually determines (availability, registration, DNS), so a reader must infer the resource semantics from check_domain or the only_available parameter.

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 explicit triggering guidance: 'Зовите его, когда доменов больше одного', and it claims the batch approach is noticeably faster than checking 'по одному', which implicitly routes single-domain calls to check_domain. The alternative is described by behavior rather than by tool name, so the routing is clear but not fully explicit.

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